Early-Stage NSCLC: Surgery, SABR & Adjuvant Therapy — When Does Each Apply?
Your patient has a resectable lung mass. The first decision is surgery vs SABR. The second is what comes after.
Before treatment planning, confirm you have:
- CT chest/abdomen/pelvis + PET-CT (all resectable candidates)
- Pulmonary function tests (FEV1, DLCO)
- Mediastinal staging (EBUS/EUS if CT/PET suspicious)
- EGFR/ALK/ROS1/RET/MET/KRAS/BRAF/HER2/PD-L1 — mandatory before any systemic therapy
- Brain MRI (Stage II–III or if symptomatic)
- ECOG performance status + comorbidity assessment
Quick Navigation
Stage I: Surgery
Your patient has a Stage I lesion — is surgery the right first move?
Indications for Upfront Surgery
- Stage IA–IB NSCLC, technically resectable
- Adequate lung function: FEV1 ≥60% predicted, DLCO ≥60%
- No prohibitive comorbidities
- Lobectomy is standard resection for most Stage I NSCLC
- Sublobar resection (segmentectomy) acceptable for Stage IA1–IA2 (<2cm) per JCOG0802/WJOG4607L — non-inferior OS to lobectomy for ≤2cm peripheral tumors
- Mediastinal lymph node dissection (MLND) or systematic sampling — mandatory for staging accuracy
- VATS preferred over open thoracotomy where available — equivalent oncologic outcomes, less morbidity
Adjuvant Therapy After Resection
| Stage | Adjuvant Recommendation | Notes |
|---|---|---|
| Stage IA | Surveillance only | No adjuvant chemo benefit shown |
| Stage IB (≥4cm) | Adjuvant chemo — optional | LACE meta-analysis: marginal benefit; NCCN: optional |
| EGFR-mutated IB–IIIA (R0) | Adjuvant osimertinib × 3yr | ADAURA: 5yr DFS 88% vs 53%, OS benefit (HR 0.49) |
| ALK-rearranged IB–IIIA (R0) | Adjuvant alectinib × 2yr | ALINA: 2yr DFS 93.8% vs 78.4% (HR 0.24) |
| PD-L1 ≥1%, Stage II–IIIA | Chemo → adjuvant atezolizumab 1yr | IMpower010: DFS HR 0.66 |
| Any PD-L1, IB≥4cm–IIIA | Chemo → adjuvant pembrolizumab 1yr | KEYNOTE-091: DFS HR 0.76 |
Key rule: Do NOT combine adjuvant targeted therapy (osimertinib/alectinib) with adjuvant immunotherapy. Use one or the other — sequential only (chemo → targeted OR chemo → IO, never targeted + IO simultaneously).
Key Trial Data
ADAURA — Adjuvant Osimertinib in Resected EGFR-Mutated NSCLC
Design: N=682, resected Stage IB–IIIA EGFR-mutated NSCLC (Ex19del/L858R), osimertinib 80mg daily vs placebo × 3 years.
Primary endpoint (DFS, Stage II–IIIA): 5yr DFS 65% vs 29% (HR 0.23); overall population 5yr DFS 88% vs 53% (HR 0.27).
OS: Significant OS benefit (HR 0.49; p=0.0004) — first adjuvant targeted therapy to show OS benefit in NSCLC.
CNS DFS: Significantly improved (HR 0.24) — important for patients with higher CNS recurrence risk.
Status: New standard of care for resected EGFR-mutated Stage IB–IIIA NSCLC.
ALINA — Adjuvant Alectinib in Resected ALK+ NSCLC
Design: N=257, resected Stage IB–IIIA ALK-rearranged NSCLC, alectinib 600mg BID × 2yr vs chemotherapy (cisplatin doublet × 4 cycles).
Primary endpoint (DFS):2yr DFS 93.8% vs 78.4% (HR 0.24; p<0.0001).
CNS DFS: Significantly improved with alectinib — HR 0.22.
Tolerability: Alectinib was better tolerated than chemotherapy; low rates of grade ≥3 AEs.
Status: New standard of care for resected ALK+ Stage IB–IIIA NSCLC.
Stage I: SABR / SBRT
The patient is medically inoperable or refuses surgery — is SABR appropriate?
SABR/SBRT Overview
- SABR (stereotactic ablative radiotherapy) / SBRT: standard of care for medically inoperable Stage I NSCLC
- Achieves 3yr local control >90%, comparable to surgery in retrospective matched series
- Eligibility: Stage IA–IB, technically resectable but patient medically unsuitable or declines surgery; OR truly inoperable
- Dose regimens (institution-dependent): 54 Gy/3fx (peripheral), 60 Gy/5fx (central/ultra-central modifications), 50 Gy/5fx
- Contraindications: prior thoracic RT with overlapping field, active interstitial lung disease (ILD), pregnancy
High-Risk Features After SABR
- Lymphovascular invasion (LVI) — associated with higher distant recurrence
- Pleural invasion — risk factor for systemic spread
- >2cm tumors (or solid component >1cm on thin-section CT)
- Pathologic confirmation of recurrence vs radiation fibrosis: PET-CT, biopsy where safe
- Refer to thoracic oncology MDT; consider adjuvant systemic therapy (IO or targeted in driver+ tumors)
- Local recurrence after SABR: re-SBRT feasible for carefully selected patients; salvage surgery where technically feasible
Follow-up After SABR
SABR vs Surgery: Evidence Summary (JROSG10-1, STARS, ROSEL, VALOR)
Individual randomised trials (STARS, ROSEL) were closed early due to poor accrual; pooled analysis (Chang et al.) suggested comparable or superior OS with SABR in operable patients, but sample sizes were very small (N≈58 pooled).
The VALOR trial (VA Cooperative) was the largest randomised effort; also closed early due to accrual challenges. No definitive superiority established for either modality in operable Stage I.
Retrospective matched series consistently show surgery superior for operable patients; SABR superior for inoperable or high-risk surgical candidates.
MDT recommendation: surgery for operable patients; SABR for medically inoperable or patient-declined surgery. Shared decision-making is essential.
Stage II Resectable NSCLC
Stage IIA–IIB — neoadjuvant first or surgery first?
Two Guideline-Endorsed Strategies
Option A — Surgery First
Surgery → adjuvant chemo (cisplatin doublet × 4 cycles) ± adjuvant IO (if driver-negative) ± targeted therapy (if driver+). Preferred when patient is immediately resectable and fit.
Option B — Neoadjuvant Chemo-IO → Surgery
Neoadjuvant chemo + IO × 3–4 cycles → surgery → adjuvant IO × 1yr. Preferred for Stage IIB–IIIA in EGFR/ALK wild-type patients. Allows pathologic response assessment (pCR) and potential downstaging.
EGFR/ALK+ patients: Avoid neoadjuvant immunotherapy — no benefit and risk of ILD. Use neoadjuvant chemotherapy ± targeted therapy (neoadjuvant osimertinib: NeoADAURA/NEOSEI trials show high pCR rates; not yet standard of care).
Adjuvant Chemotherapy Regimens
- Preferred cisplatin doublets: cisplatin + vinorelbine (all histologies), cisplatin + pemetrexed (non-squamous), cisplatin + gemcitabine (squamous)
- Carboplatin substitution if cisplatin-ineligible (renal impairment, hearing loss, neuropathy)
- 4 cycles standard; dose reduce appropriately for toxicity
- IMpower010: After ≥1 cycle platinum chemo, atezolizumab × 1yr in PD-L1 ≥1% Stage II–IIIA → DFS HR 0.66
- KEYNOTE-091: Pembrolizumab × 1yr after chemo in Stage IB≥4cm–IIIA (unselected PD-L1) → DFS HR 0.76
Perioperative Chemo-IO
Which perioperative IO regimen — CheckMate 816, KEYNOTE-671, AEGEAN, or CheckMate 77T?
All four regimens are guideline-endorsed for resectable Stage II–IIIA NSCLC in EGFR/ALK wild-type patients. Do not use in EGFR-mutated or ALK-rearranged patients — no IO benefit, risk of ILD.
| Trial | Drug | Neoadj. | Adjuvant | pCR | EFS/DFS | Notes |
|---|---|---|---|---|---|---|
| CheckMate 816 | Nivolumab + chemo | 3 cycles | None | 24% vs 2.2% | EFS HR 0.63 | First approved; neoadjuvant only |
| KEYNOTE-671 | Pembrolizumab + chemo | 4 cycles | Pembro 1yr | 18.1% vs 4% | EFS HR 0.59 | Peri-op full cycle |
| AEGEAN | Durvalumab + chemo | 4 cycles | Durva 1yr | 17.2% vs 4.3% | EFS HR 0.68 | PD-L1 unselected |
| CheckMate 77T | Nivolumab + chemo | 4 cycles | Nivo 1yr | 25.3% vs 4.7% | EFS HR 0.58 | All comers |
Clinical selection: Any of these four regimens is acceptable per NCCN and ESMO guidelines. Choice depends on availability, reimbursement, and patient preference. If progression occurs before surgery: proceed to surgery if still resectable; switch to alternative systemic therapy if now unresectable.
CheckMate 816 — Nivolumab + Chemo (Neoadjuvant Only)
Design: N=358, Stage IB–IIIA resectable NSCLC (EGFR/ALK wild-type), nivolumab 360mg + platinum doublet × 3 cycles vs chemo × 3 cycles alone.
pCR:24.0% vs 2.2% (OR 13.94; p<0.0001). EFS HR 0.63 (95% CI 0.43–0.91).
Key features: First approved perioperative IO regimen. Neoadjuvant-only (no adjuvant IO component). Favourable surgical outcomes — no increase in surgical complications.
FDA approved May 2022. First-in-class approval for neoadjuvant IO in resectable NSCLC.
KEYNOTE-671 — Pembrolizumab + Chemo (Perioperative)
Design: N=797, Stage II–IIIB resectable NSCLC (EGFR/ALK wild-type), pembrolizumab 200mg + platinum doublet × 4 cycles → surgery → pembrolizumab × 1yr vs chemo → surgery → placebo.
pCR:18.1% vs 4.0%. EFS HR 0.59 (p<0.00001). OS HR 0.72 (p=0.0022).
FDA approved October 2023.
AEGEAN — Durvalumab + Chemo (Perioperative)
Design: N=802, Stage IIA–IIIB resectable NSCLC (EGFR/ALK wild-type), durvalumab + platinum doublet × 4 cycles → surgery → durvalumab × 1yr vs chemo → surgery → placebo.
pCR:17.2% vs 4.3% (OR 4.82; p<0.0001). EFS HR 0.68 (p=0.004).
FDA approved December 2024. PD-L1 unselected population — all comers benefited.
CheckMate 77T — Nivolumab + Chemo (Perioperative)
Design: N=461, Stage IIA–IIIB resectable NSCLC (EGFR/ALK wild-type), nivolumab + platinum doublet × 4 cycles → surgery → nivolumab × 1yr vs chemo → surgery → placebo.
pCR:25.3% vs 4.7%. EFS HR 0.58 (p<0.0001).
FDA approved November 2024. Highest numerical pCR rate among perioperative IO trials to date.
Adjuvant Therapy by Driver Mutation
Resection done — now what? The driver mutation completely changes the adjuvant plan.
| Driver | Stage | Adjuvant Recommendation | Key Trial |
|---|---|---|---|
| EGFR Ex19del/L858R | IB–IIIA (R0) | Osimertinib 80mg × 3yr (after chemo if given) | ADAURA |
| ALK rearrangement | IB–IIIA (R0) | Alectinib 600mg BID × 2yr (instead of chemo) | ALINA |
| No driver, PD-L1 ≥1% | II–IIIA (R0) | Adjuvant chemo → atezolizumab 1yr | IMpower010 |
| No driver, any PD-L1 | IB≥4cm–IIIA | Adjuvant chemo → pembrolizumab 1yr | KEYNOTE-091 |
| No driver, PD-L1 <1% | II–IIIA | Adjuvant chemo alone (no IO benefit confirmed) | — |
| EGFR exon 20 ins / uncommon | IB–IIIA | Adjuvant chemo; targeted adjuvant not yet standard | — |
Critical sequencing rule: NEVER combine adjuvant targeted therapy with adjuvant immunotherapy. Use sequential only: chemo → targeted therapy OR chemo → IO. Targeted + IO simultaneous combination increases toxicity with no proven benefit.
Clinical FAQs
Common clinical dilemmas — what does the evidence actually say?
Segmentectomy or lobectomy for Stage IA ≤2cm?
JCOG0802/WJOG4607L demonstrated segmentectomy is non-inferior to lobectomy for ≤2cm peripheral tumors in overall survival. Lobectomy remains preferred for central tumors or when achieving adequate surgical margins is uncertain. Mediastinal lymph node sampling must be performed regardless of resection type.
Can I use neoadjuvant immunotherapy in EGFR-mutated patients?
No. EGFR/ALK+ patients should not receive neoadjuvant immunotherapy — there is no PFS benefit demonstrated and there is a clinically significant risk of immune-mediated ILD. For EGFR+ patients requiring neoadjuvant treatment, use platinum-based chemotherapy ± neoadjuvant osimertinib (NeoADAURA, NEOSEI trials show high pCR but are not yet standard-of-care).
Which perioperative IO regimen is preferred?
All four regimens (CheckMate 816, KEYNOTE-671, AEGEAN, CheckMate 77T) are guideline-supported for resectable Stage II–IIIA EGFR/ALK wild-type NSCLC. CheckMate 816 is neoadjuvant-only (no adjuvant IO); KEYNOTE-671, AEGEAN, and CheckMate 77T each include 1 year of adjuvant immunotherapy. Selection should be based on local availability, reimbursement, and patient preference.
How long do I give adjuvant osimertinib?
3 years per ADAURA protocol. Do not restart osimertinib immediately at local recurrence — manage according to metastatic EGFR protocols. If metastatic recurrence occurs after completing adjuvant osimertinib, re-challenge is appropriate and molecular re-testing for resistance mechanisms (T790M, C797S) should be performed.
Do I need to test PD-L1 for adjuvant IO selection?
IMpower010 (atezolizumab) requires PD-L1 ≥1% (SP142 assay) for demonstrated DFS benefit in Stage II–IIIA. KEYNOTE-091 (pembrolizumab) showed DFS benefit in the unselected Stage IB≥4cm–IIIA population regardless of PD-L1 expression, though benefit was numerically larger with PD-L1 ≥50%. PD-L1 testing is strongly recommended but does not universally gate adjuvant IO use depending on the chosen agent.
Is PORT (postoperative radiotherapy) still indicated?
No. The Lung-ART randomised trial definitively showed that PORT did not improve OS in completely resected N2 NSCLC and was associated with increased cardiovascular and pulmonary toxicity. PORT is no longer standard of care after complete resection, even in N2 disease. PORT may still be considered after R1/R2 resection in selected cases after MDT discussion.
Surgery — Decision & Technique
Who gets upfront surgery, what resection type, and how do we dissect the nodes?
Indications for Upfront Surgery (2026 Landscape)
In the 2026 treatment landscape, the “upfront surgery first” approach has narrowed significantly due to the success of perioperative immunotherapy. However, it remains the definitive gold standard for specific patients per ESMO 2026, NCCN 2026, and UpToDate.
Clinical Stage IA & IB (T1a–T2a, N0)
For tumors ≤4 cm with node-negative mediastinum confirmed by PET-CT and EBUS, upfront surgery is the preferred management.
Segmentectomy: Based on CALGB 140503 and JCOG0802 (confirmed 2025), segmentectomy is equivalent to lobectomy for peripheral tumors ≤2 cm (T1a/b) with confirmed N0 status.
Lobectomy: Remains standard for tumors 2–4 cm or those that are not peripheral.
When to Choose Upfront Surgery for Stage II–III
- Active autoimmune disease (Grade 3/4 colitis, myasthenia gravis) — neoadjuvant CPI unsafe
- Organ transplant — chronic immunosuppression, high graft rejection risk with IO
- Known EGFR/ALK mutations — avoid neoadjuvant IO; plan ADAURA/ALINA post-surgery
- Patient refusal of 9–12 week neoadjuvant delay
- Indeterminate node — negative EBUS but persistent suspicion; intraoperative frozen section
One-line exam summary: Upfront surgery is indicated for Stage IA/IB (T1–T2aN0) disease or Stage II/III cases where immunotherapy is contraindicated or driven by EGFR/ALK mutations.
VATS L-MLND — Definition and Trial Role
Video-Assisted Thoracoscopic Surgery Lobectomy and Mediastinal Lymph Node Dissection (VATS L-MLND) is the surgical gold standard for operable Stage I–II NSCLC. It combines minimally invasive approach with systematic clearance of mediastinal lymph nodes.
MLND — Nodal Stations Required:
Right-sided tumor:
Stations 2R, 4R, 7, 8, 9 (+ hilar N1 stations)
Left-sided tumor:
Stations 4L, 5, 6, 7, 8, 9 (+ hilar N1 stations)
Note: Unlike simple nodal “sampling,” MLND requires removal of all lymphatic tissue within specified anatomical boundaries.
Revised STARS Trial (10-Year Update 2026) — VATS L-MLND Cohort
Design: 80 patients receiving SABR vs 80 patients undergoing VATS L-MLND at MD Anderson (propensity score matched).
10-Year Outcomes:
| Endpoint | SABR | VATS L-MLND |
|---|---|---|
| Overall Survival (OS) | 69% | 66% |
| Cancer-Specific Survival (CSS) | 92% | 89% |
| Recurrence-Free Survival (RFS) | 57% | 65% |
| Grade ≥3 short-term complications | ~1% | ~50% |
Key interpretation: VATS L-MLND showed superior RFS but this did not translate to an OS advantage. The surgical cohort’s primary advantage is pathological staging — up to 10–15% of patients are upstaged to Stage II/III, triggering adjuvant therapy that improves long-term CSS.
For a fit patient, VATS L-MLND remains the standard because superior pathological staging identifies patients who require adjuvant systemic therapy.
Viva Cases — Surgery Decision
Case 1: A 68-year-old female, 15 pack-year smoker, has a 1.8 cm peripheral nodule in the Left Lower Lobe. PET is cold in the mediastinum. What is your surgical plan?
Case 2: A patient has a 4.5 cm RUL mass (Stage IIA). EBUS is negative. They have active Crohn's disease managed with biologics. Do you offer neoadjuvant chemo-IO?
Case 3: A 55-year-old non-smoker has a 5 cm tumor (Stage IIB). Biopsy confirms adenocarcinoma with EGFR Exon 19 deletion. Upfront surgery or neoadjuvant chemo-IO?
Case 4: A patient has a 3 cm tumor involving the origin of the RUL bronchus. N0 on PET. Do you proceed to surgery?
Case 5: You perform an upfront lobectomy for a clinical T2aN0 patient. Final pathology shows pT2aN1, Stage IIB. What next?
SABR — Patient Selection & Delivery
All indications, contraindications, tumor location definitions, and FEV1 thresholds for SABR.
SABR Indications (NCCN v2.2026 / ESMO 2026)
1. Standard of Care — Medically Inoperable Patients
Clinical Stage I or IIA (node-negative, tumor ≤5 cm) who cannot tolerate surgery due to comorbidities.
Inoperability criteria:
- • Lung function: FEV1 <1L or <40% predicted
- • DLCO <40% predicted
- • Cardiovascular: recent MI (within 3 months) or severe heart failure/unstable angina
- • Significant age-related frailty or multiple comorbidities (severe COPD, renal failure)
2. Patient Preference — Medically Operable but Declining Surgery
Patients who are surgical candidates but refuse an invasive procedure. Revised STARS Trial (10-year update, late 2025) solidified this as an evidence-based option: 10-year OS 69% for SABR vs 66% for VATS lobectomy for Stage I NSCLC <3 cm.
3. Technical Prerequisites
- • Integrated PET-CT + Brain MRI mandatory to confirm Stage I status
- • Histological confirmation preferred but not mandatory if MDT confirms high pre-test probability and surgery not an option
Tumor Location — Definitions & Fractionation
| Location | Definition | Standard Fractionation | Key Risk |
|---|---|---|---|
| Peripheral | >2 cm from proximal bronchial tree (PBT) in all directions | 54 Gy/3fx or 48 Gy/4fx | Minimal if V20 low |
| Central | ≤2 cm from PBT or adjacent to mediastinal pleura. PBT = distal 2 cm of trachea + right/left main bronchi + lobar bronchi | 50 Gy/5fx (RTOG 0813) | Bronchial stenosis, airway necrosis, vessel hemorrhage |
| Ultra-Central | PTV overlaps or touches trachea, main bronchi, esophagus, heart, or great vessels | 60 Gy/10–12fx (HILUS trial: 8fx had 15% fatal hemorrhage) | Fatal hemorrhage — extreme caution |
| Chest Wall–Abutting | Touching or very close to ribs/pleura | 50–55 Gy/5fx preferred over 3fx | Rib fracture (10–15%), chronic chest wall pain |
| Apical (Pancoast) | Very top of lung | 5–10 fractions; brachial plexus Dmax <30 Gy/3–5fx | Brachial plexopathy |
HILUS trial (2026 update): Ultra-central tumors treated with 8-fraction SABR had up to 15% rates of fatal hemorrhage. Current guidelines recommend 10–15 fractions for ultra-central disease. Never use a 3-fraction ablative regimen for central or ultra-central tumors.
FEV1 and SABR Eligibility
No Absolute FEV1 Minimum
Unlike surgical resection (FEV1 >1.5L required for lobectomy), there is no absolute minimum FEV1 or DLCO threshold for SABR. Patients with severe emphysema and FEV1 <40% predicted tolerate SABR well with minimal impact on global lung function (RTOG trials, 2025 meta-analyses).
Even patients on home oxygen (nasal cannula) can safely undergo SABR for peripheral tumors with small treatment volume.
The Real Limitation — ILD
While low FEV1 (COPD/obstructive) is not a barrier, Interstitial Lung Disease (ILD/IPF) is a major relative contraindication. Patients with ILD have up to 15–20% risk of fatal Radiation Pneumonitis after SABR regardless of FEV1.
Primary safety metric: V20 (volume of total lung receiving 20 Gy). Keep V20 <10–15%. At very low FEV1, aim for V20 <5–10%.
Patient A has FEV1 45% (COPD) — low risk for SABR. Patient B has FEV1 85% but has IPF — much higher risk. Low FEV1 from COPD is well-tolerated; ILD is the dangerous contraindication.
Viva Cases — SABR Indications
Case 1: A 75-year-old with a 2.5 cm peripheral nodule has an FEV1 of 1.1L and DLCO of 35%. What is your recommendation?
Case 2: A fit 60-year-old with a T1bN0 tumor (2.0 cm) refuses surgery. How do you counsel them?
Case 3: A patient has a 3.5 cm tumor located 1 cm from the right main bronchus. Can you use standard 3-fraction SABR?
Case 4: An 82-year-old with a PET-avid 2 cm growing nodule is too frail for biopsy. Can you still offer SABR?
Case 5: A surgeon argues SABR is inferior because it doesn't clean the nodes. How do you respond?
Post-Treatment Follow-up
How to monitor after SABR — schedule, imaging, RILI vs recurrence, and Huang high-risk features.
Follow-up Schedule (NCCN v2.2026 / ESMO 2026)
Post-SABR surveillance is front-loaded because most local failures and distant metastases occur within the first 24 months.
| Time Period | Imaging | Notes |
|---|---|---|
| Years 1–2 | CT Chest (with contrast) every 3–6 months | Most local failures and distant mets occur here |
| Years 3–5 | CT Chest every 6 months | Compare to nadir scan, not just previous scan |
| Year 5+ | Annual Low-Dose CT (LDCT) | Second primary lung cancer risk (1–2%/yr) now outweighs original recurrence risk |
PET-CT is NOT recommended for routine surveillance. SABR causes inflammation that can remain PET-avid for up to 2 years. Only order PET-CT if you see an actionable High-Risk Feature (HRF) on CT. The 6-month PET rule: if you must do a PET-CT, wait at least 6 months post-SABR to minimise false positives from radiation pneumonitis.
Three Phases of Radiation-Induced Lung Injury (RILI)
Phase 1: Acute (0–3 months)
Usually nothing visible, or faint ground-glass haze.
Phase 2: Pneumonitis (3–9 months)
Patchy consolidation often larger than original tumor. Do not panic — this is almost always inflammation.
Phase 3: Fibrosis (>9 months)
Lung shrivels into a dense, linear scar. Should remain stable or slowly shrink over time.
Action Triggers — When Routine Follow-up Stops
| Observation | Action |
|---|---|
| Stable or shrinking scar | Continue routine follow-up |
| New “bulging” margin | Short-interval CT (3 months) or PET-CT |
| Sequential growth (>20%) | Mandatory PET-CT and consider biopsy |
| Late growth (>12 months) | High suspicion for recurrence; refer to MDT |
Huang High-Risk Features (HRFs) — Full Reference
The presence of ≥3 HRFs is highly suggestive of local recurrence(sensitivity/specificity >90%) per Huang et al. and Senthi et al., incorporated into NCCN v2.2026 and ESMO guidelines. Traditional RECIST 1.1 criteria are often inadequate due to expected volumetric expansion of the fibrotic scar.
The “Big Six” Huang CT High-Risk Features:
Sequential Enlargement
Progressive increase in size on at least two consecutive scans. This is the most sensitive predictor of recurrence. Size increases within the first year can occur as lung collapses into the fibrotic zone — must be sequential (occurring again at the next scan).
Bulging Margin
A focal convex change in the border of the fibrotic area. Fibrosis is usually linear or concave; a convex or rounded shape is actionable. The transition from concave/flat scar margin into a convex/rounded shape is the classic HRF.
Disappearance of Air Bronchograms
Air bronchograms are common in radiation fibrosis (patent airways). Their disappearance or filling-in suggests a solid tumor is obstructing or infiltrating the airway. Highly specific for local recurrence.
Enlargement After 12 Months
Any growth occurring more than 1 year post-SABR is the strongest individual predictor of recurrence, as radiation-induced changes usually stabilise within 12–18 months.
Loss of Linear Margins
Fibrosis often has sharp, straight-line edges corresponding to the radiation beam. A shift to shaggy, spiculated, globular, or lobulated margins is actionable.
Pleural Thickening or Effusion
New or progressive thickening of the pleura adjacent to the treated area, or development of a localized effusion (focal pleural-based mass or effusion rather than linear pleural thickening).
PET-CT Actionable Criteria (2026 Standard)
| Feature | Interpretation | Actionable Threshold |
|---|---|---|
| Early PET (<6 months) | Often unreliable due to pneumonitis | Avoid definitive decisions based on SUV alone |
| Late PET (>12 months) | Inflammation should have subsided | SUVmax >5.0 or significant rise from post-SABR nadir |
| Uptake pattern | Diffuse vs mass-like uptake | Intense, focal “mass-like” uptake is highly suspicious; diffuse low-level = pneumonitis |
Benign vs Suspicious — Differentiation Table
| Feature | Radiation Fibrosis (Benign) | Local Recurrence (Actionable) |
|---|---|---|
| Time of appearance | 6–24 months (stabilises after 2yr) | Can occur anytime; suspicious if after 1yr |
| Volume trend | Initial increase, then contraction | Continuous, progressive enlargement |
| Margin | Sharp, linear, or stellate | Bulging, rounded, or lobulated |
| Bronchograms | Persistent or “stretching” (traction) | Complete loss/obstruction |
| Pleura | Linear pleural thickening | Focal pleural-based mass or effusion |
Clinical Management Pathway (2026 Standard)
Low Suspicion (0–1 HRF)
Continue standard CT surveillance (every 3–6 months).
Moderate Suspicion (2 HRFs)
Short-interval CT (8–12 weeks) or FDG-PET/CT if >12 months post-treatment.
High Suspicion (≥3 HRFs or SUVmax >5.0)
Mandatory MDT discussion. Biopsy confirmation if salvage planned. Note: biopsies in fibrotic zones can yield high false-negative rates — “growth over time” remains a valid surrogate for recurrence in inoperable patients.
Baseline matters:Always compare the current scan to the “Nadir” scan (the scan where the scar was at its smallest), not just the previous scan. Recurrence is often subtle and only obvious when compared to the nadir.
Viva Cases — High-Risk Features
Case 1: CT at 9 months shows 20% increase in diameter of fibrotic area compared to the 3-month scan. Is this recurrence?
Case 2: At 18 months, air bronchograms previously present in the radiation scar have disappeared. What is your concern?
Case 3: PET-CT at 6 months shows SUVmax of 4.2. How do you interpret this?
Case 4: A new small pleural effusion and 1 cm of pleural thickening adjacent to a SABR site treated 2 years ago. What is your move?
Case 5: A patient has two HRFs (sequential enlargement and bulging margin) but SUVmax is only 3.5. Biopsy or observe?
Decision Framework — Surgery vs SABR
Your patient has actionable HRFs or suspected post-SABR recurrence — here is the full algorithm.
The Decision Tree: From Suspicion to Action
When actionable radiological features (HRFs) are identified — or when choosing between surgery and SABR de novo — the 2026 clinical landscape requires a structured salvage-oriented workflow.
Step 1: MDT Review (Before Any Intervention)
A dedicated “SABR MDT” requires a thoracic radiologist, radiation oncologist, and thoracic surgeon to assess the trajectory of scans.
The question:Is growth “congruent” with the high-dose region, or is it a marginal miss? Marginal misses are easier to salvage surgically.
Step 2: Tissue Confirmation (Gold Standard)
Biopsy is required if the patient is a candidate for aggressive salvage:
- • CT-Guided Biopsy: Best for peripheral lesions
- • EBUS/Bronchoscopy: Essential if HRFs include disappearing air bronchogram or central growth
- • Liquid Biopsy (ctDNA): In 2026, rising ctDNA alongside a suspicious scan is an increasingly accepted action signal, even if biopsy is non-diagnostic
Step 3: Restaging (PET-CT + Brain MRI)
If recurrence confirmed, ensure disease has not spread. If distant metastases present, local salvage is no longer the priority — systemic therapy takes precedence.
Salvage Options — Choosing the Rescue Therapy
| Option | Best For | Key Consideration (2026) |
|---|---|---|
| Salvage Surgery | Fit patients; marginal failures | Gold standard. Technically “sticky” due to fibrosis, but best chance at long-term survival. Mention bronchial stump flap to prevent bronchopleural fistula in irradiated tissue. |
| Salvage Re-SABR | Unfit for surgery; peripheral recurrence | High risk of cumulative toxicity. Use caution if new target overlaps old high-dose isodose lines. Protracted schedule (10–15fx) essential. |
| Thermal Ablation | Small nodules (<2 cm); central-ish locations | Good middle ground for patients too frail for surgery but too high-risk for more radiation. Radiation-blind — no cumulative dose limit. |
| Systemic Therapy | Broad failure or high-risk pathology | Lean heavily on IO or TKIs if actionable mutation present. Systemic first if distant mets confirmed on restaging. |
The “Rule of Two” for Empirical Salvage (when biopsy impossible):
If you have two or more HRFs (e.g., sequential enlargement AND bulging margin) plus a rising SUVmax >5.0, current 2026 consensus allows salvage treatment without a biopsy, provided the MDT agrees the probability of recurrence is >90%.
Don’t forget the brain: A common oral exam trap is forgetting to re-image the brain before committing to an aggressive local salvage procedure. Always Brain MRI before salvage surgery or re-SABR.
Ablation for Early-Stage NSCLC
When does thermal ablation outperform SABR — modalities, indications, and the 2026 frontier.
In the 2026 management hierarchy for Stage I NSCLC, thermal ablationhas solidified its role as a vital “third-line” local therapy — the go-to tool when both surgery and SABR have failed or are contraindicated.
Core Modalities
Microwave Ablation (MWA)
The current workhorse. Uses electromagnetic waves to create heat. Faster, reaches higher temperatures, less affected by heat-sink effect from nearby blood vessels.
Radiofrequency Ablation (RFA)
The “classic” version. Uses high-frequency alternating current. Effective but struggles with larger tumors and lesions near major vessels.
Cryoablation
Freeze-thaw method using argon/helium. Preserves collagenous architecture — safer for tumors near pleura or chest wall (less pain) and major airways.
When to Choose Ablation over SABR
- The “Cumulative Dose” Ceiling: Prior SABR to the same or nearby area; patient has reached maximum safe radiation dose to chest wall or lung. Ablation is radiation-blind — no cumulative dose limit.
- Multiple Primary Tumors:Multifocal ground-glass opacities (GGOs) or synchronous Stage I tumors — ablation can “pick off” nodules while preserving lung function.
- Ultra-Peripheral Pleurisy Risk: If tumor touches the ribs, SABR can cause chronic chest wall pain or rib fractures. Cryoablation is often better tolerated here.
- Patient Preference — One and Done: SABR takes 3–15 visits; ablation is a single procedure, often under conscious sedation or short general anaesthesia.
Outcomes & Comparison
| Feature | Surgery (Lobectomy) | SABR | Thermal Ablation |
|---|---|---|---|
| Local Control | 95% | 90–93% | 80–85% (excellent if <2 cm) |
| Recovery | Weeks | None (outpatient) | 1–2 days |
| Main Risk | Perioperative death | Pneumonitis | Pneumothorax (30–50%) |
| Invasiveness | High | Zero | Moderate (needle) |
| 2-yr OS (inoperable) | — | ~85–90% | ~70–80% (SOLSTICE, MWA registries) |
Pneumothorax risk:Roughly 30–50% of patients will develop a pneumothorax during the needle stick, and approximately 10–15% will require a chest tube. This must be disclosed in pre-procedure counselling. For tumors >3 cm, recurrence rate climbs significantly compared to SABR — ablation is best reserved for tumors <2–3 cm.
The 2026 Frontier — Bronchoscopic Ablation
Robotic Bronchoscopy + Ablation (Emerging)
The biggest shift in the last two years: navigating a catheter through the natural airways to the tumor and deploying microwave or Pulsed Electric Field (PEF) energy.
Benefit: Zero risk of pneumothorax.
Status:Currently reserved for specialised centres. NCCN 2026 recognises it as an emerging “lung-sparing” technology.
Managing Recurrence After SABR / Surgery
Isolated local recurrence has a 5-year OS nearly identical to patients who never recurred (~58%) — if successfully salvaged.
1. Diagnostic Triage
Before selecting a salvage modality, prove the recurrence is isolated and biopsy-confirmed.
- Restaging: Mandatory PET-CT and Brain MRI. If regional nodes are involved (isolated regional recurrence, iRRs), 5-yr OS drops to ~31% and management shifts toward Stage III protocols (chemo-RT).
- Biopsy: Essential to distinguish recurrence from Radiation-Induced Lung Injury (RILI).
- Liquid Biopsy (ctDNA):In 2026, a rising ctDNA titer alongside an indeterminate “bulge” on CT is an increasingly accepted action signal for recurrence, even if biopsy is non-diagnostic.
2. Salvage Surgery — Gold Standard
Outcome data (NCDB 2026): For post-SABR failure, salvage lobectomy provides a 5-year OS of ~50%.
Technical considerations:
- • The “woody” or “sticky” hilum caused by prior radiation makes these cases complex
- • Anatomic resection (lobectomy) preferred over wedge to ensure R0 margins and nodal clearance
- • VATS/Robotics feasible in ~75% of cases in expert centres; low threshold for conversion to open thoracotomy
- • Pro tip: Mention the use of a bronchial stump flap (intercostal muscle or omentum) to prevent bronchopleural fistulas in irradiated tissue
3. Salvage Re-SBRT
Used for patients who remain medically inoperable or refuse a second surgery.
Eligibility Criteria
- • Absence of distant disease (PET-CT + Brain MRI)
- • Recurrence at least 6–12 months after initial SBRT
- • Adequate performance status to tolerate late toxicity
- • Peripheral location preferred (central is high-risk)
Dose & Fractionation
Common re-SBRT regimen: 40–50 Gy in 8–10 fractions.
Protracted schedule allows healthy tissue to repair. You must import the original treatment plan and calculate cumulative EQD2 to all organs at risk — not just the new dose in isolation.
2-year local control: 60–81%.
Re-SBRT — Cumulative EQD2 Dose Limits (2026)
| Organ at Risk | Cumulative EQD2 Limit | Consequence of Overdose |
|---|---|---|
| Chest Wall | 120–150 Gy | Chronic pain, rib fracture |
| Esophagus | 80–100 Gy | Stricture, tracheoesophageal fistula |
| Main Bronchi | 100–120 Gy | Atelectasis, fatal hemorrhage |
| Spinal Cord | 50–60 Gy | Myelopathy (paralysis) |
Central/Ultra-Central Recurrence — Re-SBRT is often a “Hard Stop”: Re-irradiating a tumor touching the main bronchi or trachea carries a significantly elevated risk of fatal airway necrosis or massive hemoptysis (HILUS trial and long-term re-irradiation data). If ultra-central, strongly consider microwave ablation or systemic therapy instead.
4. Salvage Hierarchy — MDT Decision Tool
| Scenario | Preferred Action | Rationale |
|---|---|---|
| Fit patient, peripheral LR | Salvage lobectomy | Best R0 rate and nodal staging |
| Unfit for surgery, peripheral LR | Re-SBRT or MWA | High local control with minimal recovery time |
| Central LR, prior SABR | Salvage surgery | High risk of airway death with re-SBRT |
| Multifocal recurrence | Systemic therapy ± LAT | Likely field cancerization or systemic failure |
Viva Cases — Managing Recurrence
Case 1: A patient has isolated local recurrence after SABR. They are fit, 65 years old. What is your approach?
Case 2: A patient had SABR 14 months ago and has confirmed peripheral local recurrence 1.8 cm in size. They are now too frail for surgery. What do you offer?
Case 3: The local recurrence after SABR is found to have an EGFR mutation on rebiopsy. Do you prioritise local salvage or switch to a TKI?
NSCLC 9th Edition Staging (IASLC)
Key changes from 8th to 9th edition — N2a/N2b, M1c subdivisions, and downstaged groups.
The IASLC 9th Edition TNM Classification (published 2024/2025, implemented 2026) introduces critical N2 subdivisions that directly impact resectability decisions and treatment pathways.
T Descriptors (9th Edition)
| T Stage | Definition |
|---|---|
| T1mi | Minimally invasive adenocarcinoma |
| T1a | Tumor ≤1 cm |
| T1b | Tumor >1 cm, ≤2 cm |
| T1c | Tumor >2 cm, ≤3 cm |
| T2a | Tumor >3 cm, ≤4 cm (or involves main bronchus, invades visceral pleura, or causes atelectasis) |
| T2b | Tumor >4 cm, ≤5 cm |
| T3 | Tumor >5 cm, ≤7 cm; OR invades parietal pleura, chest wall, phrenic nerve, or parietal pericardium; OR separate tumor nodule same lobe |
| T4 | Tumor >7 cm; OR invades mediastinum, heart, great vessels, trachea, recurrent laryngeal nerve, esophagus, vertebral body, or carina; OR separate nodule different ipsilateral lobe |
N Descriptors — The Critical 9th Edition Change
The 9th Edition introduces the N2a/N2b subdivision — a landmark change that downstages single-station N2 disease.
N2a — Single Station N2
Metastasis in a single ipsilateral mediastinal/subcarinal lymph node station.
Stage impact:
- • T1N2a → Stage IIB (was IIIA in 8th edition)
- • T2N2a → Stage IIIA
- • T3N2a → Stage IIIA
N2b — Multi-Station N2
Metastasis in multiple ipsilateral mediastinal/subcarinal lymph node stations.
Stage impact:
- • T2N2b → Stage IIIB
- • T3N2b → Stage IIIB
- • T4N2b → Stage IIIB
Key Staging Group Changes (8th → 9th Edition)
| TNM | 8th Edition Stage | 9th Edition Stage | Clinical Impact |
|---|---|---|---|
| T1N1 | IIB | IIA | Downstaged — still resectable |
| T1N2a | IIIA | IIB | Major — may shift toward surgical pathway |
| T3N2a | IIIB | IIIA | Downstaged — eligible for perioperative IO trials |
| T2N2b | IIIA | IIIB | Upstaged — less likely to be offered primary resection |
| M1c1 (single organ) | IVB | IVB | Subdivision from M1c2 — worse prognosis in M1c2 (multi-organ) |
One-line exam summary: The IASLC 9th Edition downstages single-station N2 (N2a) and T1N1 while introducing M1c1/M1c2 subdivisions to better reflect survival benefits seen with modern systemic therapies.
Viva Cases — 9th Edition Staging
Case 1: A 62-year-old has a 2.5 cm upper lobe mass and a single 1.2 cm station 4R lymph node positive on EBUS. No distant spread. What is the 9th Edition stage?
Case 2: A patient has a 3.5 cm tumor and biopsy-proven involvement of stations 4R and 7. What is the stage and standard of care?
Case 3: You resect a 4.5 cm adenocarcinoma (T2bN0M0, Stage IIA). Pathology shows an ALK rearrangement. What is your adjuvant recommendation?
Case 4: A patient presents with multiple liver metastases and multiple bone metastases. How do you classify this in 2026?
Case 5: A 6 cm tumor is invading the parietal pleura but not the chest wall. No positive nodes. What is the stage?
Resectable Stage II–III — Full Adjuvant & Perioperative Guide
STAS, PORT, adjuvant chemo/TKI/IO, the ADAURA chemo dilemma, ALINA vs ELEVATE, and peri-op options compared.
High-Risk Pathological Features — STAS
Spread Through Air Spaces (STAS)
STAS is defined as micropapillary clusters, solid nests, or single cells spreading through the air spaces beyond the edge of the main tumor. It is a recognized high-risk morphological feature of invasion in resected NSCLC.
- • Associated with significantly higher rates of locoregional recurrence after sublobar resection
- • STAS-positive tumors may warrant lobectomy over segmentectomy even if size criteria would support parenchymal-sparing resection
- • Positive STAS status should prompt discussion of adjuvant systemic therapy at lower stage thresholds
- • Considered in the MDT when discussing PORT candidacy (though PORT remains non-standard after Lung-ART)
PORT — Current Standard (or Non-Standard)
PORT is NOT standard of care after complete resection (R0). The Lung-ART randomised trial showed PORT did not improve OS in completely resected N2 NSCLC and was associated with increased cardiovascular and pulmonary toxicity. PORT may still be considered after R1/R2 resection in selected cases following MDT discussion.
PORT for Persistent N2 (yN2) After Perioperative Treatment
In patients who received neoadjuvant chemo-IO and are found to have residual N2 disease on final pathology (yN2), the role of PORT is under active investigation. Current 2026 guidelines do not mandate PORT even in this context, but institutional MDT discussion is recommended. The presence of yN2 disease despite neoadjuvant IO typically prompts: continuation of adjuvant IO (if perioperative regimen) and discussion of clinical trial enrollment.
Adjuvant Systemic Therapy — Complete Framework
| Stage After Surgery | Driver | Adjuvant Recommendation | Trial |
|---|---|---|---|
| IA | Any | Surveillance only — no adjuvant chemo benefit shown | — |
| IB (≥4 cm) | Wild-type | Adjuvant chemo optional (marginal benefit) | LACE meta-analysis |
| IB–IIIA (R0) | EGFR Ex19del/L858R | Adjuvant osimertinib 80mg × 3yr (after chemo if given) | ADAURA |
| IB–IIIA (R0) | ALK rearrangement | Adjuvant alectinib 600mg BID × 2yr (instead of chemo) | ALINA |
| II–IIIA | Wild-type, PD-L1 ≥1% | Cisplatin doublet chemo × 4 → atezolizumab 1yr | IMpower010 |
| IB≥4cm–IIIA | Wild-type, any PD-L1 | Cisplatin doublet chemo × 4 → pembrolizumab 1yr | KEYNOTE-091 |
The ADAURA 'Chemo Dilemma' (2026 Update)
In the ADAURA trial, adjuvant chemotherapy was optional for all enrolled patients — approximately 60% of patients received adjuvant chemotherapy before starting osimertinib. The OS benefit of osimertinib (HR 0.49) was maintained regardless of whether patients received prior adjuvant chemotherapy.
The 2026 dilemma: Should EGFR-mutant patients with Stage IB–IIIA receive adjuvant chemotherapy before osimertinib, given that osimertinib alone provides substantial OS benefit?
Arguments FOR adjuvant chemo before osimertinib:
- • Eliminates micrometastatic disease via different mechanism of action
- • Some data suggest improved outcomes for Stage IIIA patients specifically
- • Prevents resistance selection pressure from osimertinib as sole therapy
- • NCCN and ESMO both support adjuvant chemo followed by osimertinib for Stage II–IIIA
Arguments AGAINST (osimertinib alone):
- • ADAURA OS benefit (HR 0.49) achieved with or without prior chemo
- • Elderly, frail, or cisplatin-ineligible patients may not tolerate chemo
- • Stage IA/IB patients: adjuvant chemo benefit already marginal
- • Avoids 4 months of platinum toxicity (neuropathy, nephrotoxicity)
2026 consensus: adjuvant chemo → osimertinib for fit Stage II–IIIA. Osimertinib alone is acceptable for Stage IB, elderly, or cisplatin-ineligible patients.
ALINA vs ELEVATE — The Comparison Gap
| Feature | ALINA (Alectinib) | ELEVATE (Ensartinib) |
|---|---|---|
| Drug | Alectinib 600mg BID | Ensartinib 225mg QD |
| Stage | IB–IIIA (R0) | IA–IIIA (R0) |
| Duration | 2 years | 2 years |
| Comparator | Cisplatin doublet chemo × 4 cycles | Observation |
| DFS HR | 0.24 (p<0.0001) | Awaited (trial ongoing) |
| 2-yr DFS (TKI arm) | 93.8% | Preliminary data awaited |
| CNS DFS | HR 0.22 — significant benefit | Not yet reported |
| FDA status | Approved (adjuvant ALK+ NSCLC) | Not approved; trial ongoing |
| Key gap | Compared to chemo — not placebo | No head-to-head vs alectinib; different comparator |
The comparison gap: ALINA compared alectinib to chemotherapy (not placebo). ELEVATE compares ensartinib to observation. These trials cannot be directly compared due to different control arms. Alectinib remains the current standard for adjuvant ALK+ NSCLC.
Neoadjuvant/Peri-operative Chemo-IO Options — Comparison
For EGFR/ALK wild-type resectable Stage II–IIIA NSCLC. All four regimens are guideline-endorsed. Select based on local availability, reimbursement, and institutional preference.
| Trial | Drug | Neo. Cycles | Adj. IO | pCR | EFS HR | OS benefit? | FDA Approved |
|---|---|---|---|---|---|---|---|
| CheckMate 816 | Nivo + chemo | 3 | None | 24% vs 2.2% | 0.63 | Immature | May 2022 |
| KEYNOTE-671 | Pembro + chemo | 4 | Pembro 1yr | 18.1% vs 4% | 0.59 | HR 0.72 (p=0.002) | Oct 2023 |
| AEGEAN | Durva + chemo | 4 | Durva 1yr | 17.2% vs 4.3% | 0.68 | Immature | Dec 2024 |
| CheckMate 77T | Nivo + chemo | 4 | Nivo 1yr | 25.3% vs 4.7% | 0.58 | Immature | Nov 2024 |
EGFR/ALK+ patients: Do NOT offer neoadjuvant immunotherapy. There is no pCR benefit in EGFR-mutant NSCLC with IO (low pCR ~3–5%), and there is a significant risk of immune-mediated ILD that can preclude switching to TKI therapy post-surgery. Plan upfront surgery followed by adjuvant osimertinib (EGFR) or alectinib (ALK).
Neoadjuvant Therapy Response Assessment
- Pathologic Complete Response (pCR): No viable tumor in resected specimen. Strongly correlates with improved EFS and OS. pCR rates of 24–25% achieved with nivolumab-based regimens.
- Major Pathologic Response (MPR):≤10% viable tumor remaining. An intermediate endpoint that is prognostically favorable even if pCR not achieved.
- Nodal downstaging: One of the strongest prognostic markers in neoadjuvant NSCLC — conversion from N2 to N0 is associated with significantly improved long-term survival.
- ctDNA clearance: In 2026, ctDNA clearance after neoadjuvant therapy is emerging as a surrogate for pathologic response and may guide adjuvant intensity decisions. Rising ctDNA post-surgery is a strong MRD signal.
Viva Cases — Resectable Stage II–III
Case 1: A 58-year-old with T2aN2a (Stage IIB, 9th edition) NSCLC — wild-type, PD-L1 60%. Upfront surgery or neoadjuvant?
Case 2: Resected Stage IIIA EGFR Ex19del. Pathology: pT2aN2a. The patient is 72 years old. What is your adjuvant plan?
Case 3: A 50-year-old with resected Stage IIIA ALK+ NSCLC. They ask about adjuvant alectinib vs chemotherapy. How do you counsel them?
Surgery — Additional Viva Cases
High-yield surgical decision cases: fragile lung function, sleeve resection, and upstaged pathology.
Oral Exam Script (High-Yield)
Cases
Case 4 (Fragile Lung Function): A patient with a 2.5 cm RUL tumor has a ppoFEV1 of 35% and DLCO of 38%. They are not a candidate for lobectomy — what is your approach?
Case 6 (The 'Upstaged' Surgery): You perform an upfront lobectomy for a clinical T2aN0 patient. Final pathology shows a 3.5 cm tumor with 2/5 N1 nodes positive (pT2aN1, Stage IIB). What is your next step?
SABR Location — Additional Viva Cases
Rib-abutting tumors, diaphragmatic motion, esophageal proximity — dose and toxicity decisions.
Case A (Rib-Abutting): A 3 cm tumor is touching the 5th rib posteriorly. What do you tell the patient about long-term side effects?
Case B (Esophageal Neighbor): A tumor is directly touching the esophagus. What is your concern and how do you mitigate it?
Case C (Diaphragmatic Motion): A 2 cm tumor is in the very base of the lower lobe, moving 2.5 cm with respiration. How does location affect your SABR delivery?
Case D (Pancoast Presentation): An 80-year-old inoperable patient has a 2.5 cm apical tumor. They already have some tingling in their hand. What are your SABR considerations?
FEV1 & SABR — Additional Cases
Oxygen dependence, V20 DVH parameter, and large tumors in severely compromised lungs.
Case A (Oxygen Dependence): A patient with Stage I NSCLC is on 2L of continuous home oxygen. Is SABR safe?
Case B (Post-Treatment PFTs): The patient asks if their breathing will get worse after SABR. What does the data say?
Case C (V20 Question): You are reviewing a SABR plan for a patient with very poor lung function. Which DVH parameter is most important for safety?
Case D (Large Tumor in Poor Lungs): A patient has a 5.5 cm tumor and FEV1 of 35%. Can you use SABR?
Follow-up — Second Primary Risk & Exam Pro-Tips
A common exam trap: don't only watch the treated site — screen the entire lung for second primaries.
Second Primary Lung Cancer Risk
The Hidden Risk After Successful SABR
A common mistake in fellowship exams — and in clinical practice — is focusing only on the treated site. The 2026 data shows that Stage I survivors have a higher cumulative risk of developing a new primary lung cancer (1–2% per year) than of a local recurrence of the treated tumor after year 3–5.
- • At year 5+: transition to Annual Low-Dose CT (LDCT) screens the entire lung, not just the treated segment
- • New nodules elsewhere should be evaluated via standard Fleischner Society criteria / Lung-RADS
- • A new PET-avid nodule in a different lobe is a second primary until proven otherwise — treat as a new Stage I workup, not as metastatic disease
- • Smoking cessation remains the single most effective “follow-up intervention” for long-term survival
Oral Exam Pro-Tips for Follow-up
The Baseline (Nadir) Rule
Always compare the current scan to the "Nadir" scan — the scan where the scar was at its smallest, typically 12–18 months post-SABR — not just the previous scan. Recurrence is often subtle and only obvious when compared against the nadir. Document the nadir clearly in the clinical record.
The 6-Month PET Rule
If you must do a PET-CT, wait at least 6 months post-SABR to minimise false positives from radiation pneumonitis. An SUVmax of 2–4 at 4–6 months is almost always pneumonitis, not recurrence. Only use early PET if the clinical picture is dramatically changing (haemoptysis, new pleural effusion, constitutional symptoms).
MDT is the "Action"
If a scan is indeterminate, the correct oral exam answer is: "I would present this case at our specialised Lung SABR MDT for a consensus opinion on imaging versus biopsy." This acknowledges the complexity and ensures multi-disciplinary safety.
New Nodule in a Different Lobe
A common viva scenario: 18 months post-SABR, there is a new 1 cm nodule in a different lobe. This is most likely a second primary, not a metastasis. Management: PET-CT, EBUS if node-positive, and if truly Stage I de novo — offer SABR or surgery as per the original Stage I pathway.
High-Risk Features — Complete Reference (Huang + Senthi)
The full actionable HRF framework including cranio-caudal growth — the sixth criterion often missed in exams.
The presence of ≥3 HRFscarries sensitivity/specificity >90% for local recurrence (Huang et al., Senthi et al.). Traditional RECIST 1.1 criteria are inadequate post-SABR due to the expected volumetric expansion of the fibrotic scar. These six features represent the 2026 clinical consensus.
| # | High-Risk Feature | Radiological Appearance | Specificity |
|---|---|---|---|
| 1 | Enlarging Opacity After 12 Months | Any growth in the treatment area more than 1 year post-SABR | Very High — strongest single predictor |
| 2 | Sequential Enlarging Opacity | Sustained growth on at least two consecutive scans (even within year 1) | High — most sensitive predictor |
| 3 | Bulging Margin | Transition from concave/flat scar margin to convex/rounded shape | High — early actionable sign |
| 4 | Loss of Air Bronchograms | Disappearance or "filling in" of previously visible air bronchograms within fibrotic area | Very High — highly specific for recurrence |
| 5 | Loss of Linear Margin | Disappearance of sharp, linear beam-geometry edges; replaced by shaggy/spiculated/lobulated margins | Moderate-High |
| 6 | Cranio-Caudal Growth | Significant growth along the longitudinal (cranio-caudal) axis, not just axial expansion — suggests infiltrating tumor not following radiation geometry | Moderate — often missed; important sixth criterion |
The "Straight Line" sign is reassuring:Radiologists describing “linear opacities” and “volume loss” in the treated lobe — with sharp, beam-geometry edges — is consistent with benign radiation fibrosis. These findings do not require action beyond routine surveillance.
PET-CT Actionable Criteria — Full Table
| Feature | Interpretation | Actionable Threshold |
|---|---|---|
| Early PET (<6 months) | Often unreliable — “metabolic flare” from pneumonitis | Avoid definitive decisions based on SUV alone; repeat CT in 3 months preferred |
| Grey Zone PET (6–12 months) | Inflammation subsiding but may persist | SUVmax >5.0 AND focal/mass-like pattern needed for action |
| Late PET (>12 months) | Inflammation should have subsided — most reliable window | SUVmax >5.0 OR ≥20% rise from post-SABR nadir |
| Visual pattern | Diffuse low-level = pneumonitis; focal intense = suspicious | Intense, focal “mass-like” uptake is highly suspicious regardless of absolute SUV |
Re-SBRT — Exam Script & Hard Stop Cases
Chest wall prior rib fracture from first SABR — when is re-SBRT a hard stop?
Hard Stop Case: Recurrence located directly on the chest wall where first SABR caused a rib fracture. Do you still use Re-SBRT?
Re-SBRT at an early interval: Recurrence confirmed 4 months after initial SABR. The patient is inoperable. Do you offer Re-SBRT?
Advanced/Metastatic NSCLC — Key Trial Context (2026)
FLAURA2, MARIPOSA, PAPILLON — when early-stage patients recur or progress to Stage IV.
These trials are relevant when early-stage NSCLC patients experience systemic recurrence after surgery or SABR — or when de novo Stage IV disease is encountered during the staging workup. All trials below represent first-line metastatic data as of 2026.
| Trial | Drugs / Setting | Key Result | Status |
|---|---|---|---|
| FLAURA2 | Osimertinib + Platinum-Pemetrexed vs Osimertinib mono (EGFR-mutant, 1L) | PFS 25.5 vs 16.7 months (HR 0.62; p<0.001). OS data immature but trending positive. | Combination approved; use in fit patients with high disease burden |
| MARIPOSA | Amivantamab + Lazertinib vs Osimertinib (EGFR Ex19del/L858R, 1L) | PFS HR 0.70 (24 vs 20 months). Higher VTE, rash, hypoalbuminaemia with doublet. | Regulatory approved; use in patients who can tolerate IV/SubQ amivantamab |
| PAPILLON | Amivantamab + Chemo vs Chemo (EGFR Exon 20 insertion, 1L) | PFS 11.4 vs 6.7 months (HR 0.40; p<0.001). OS benefit confirmed. | New standard of care for EGFR Exon 20 insertion mutation 1L |
Additional Staging Viva Cases
Case (CheckMate 816 T4N0): A patient with Stage IIIA (T4N0) squamous cell carcinoma is being considered for neoadjuvant therapy. What is the 2026 standard?
Resectable II–III Deep Dive — STAS Morphology, ctDNA, NeoADAURA
Spread Through Air Spaces morphology, MRD monitoring with ctDNA, and the NeoADAURA vs ADAURA framework.
STAS — Core Morphological Features of Invasion
Spread Through Air Spaces (STAS) is a morphological pattern of invasion recognized by the WHO Classification of Thoracic Tumours (5th edition, 2021) and increasingly incorporated into 2026 surgical planning decisions.
STAS — Morphological Definition
- Micropapillary clusters: Small papillary tufts floating in the airspaces beyond the leading edge of the main tumor
- Solid nests: Small clusters of tumor cells (typically 5+ cells) floating in the air spaces of the lung parenchyma beyond the tumor boundary
- Single cells: Isolated tumor cells spreading through alveolar spaces — the most subtle and often missed STAS pattern
All three patterns must be identified in the parenchyma beyond the pushing edge of the main tumor to qualify as STAS — not within the tumor itself.
Clinical Consequences of STAS+
- • Significantly higher locoregional recurrence after sublobar resection (wedge > segmentectomy)
- • Lobby for lobectomy even if size criteria would support parenchymal-sparing resection
- • STAS+ status should lower the threshold for adjuvant systemic therapy
- • Higher rates of hematogenous distant metastasis independent of nodal stage
Prognostic Data (2026)
- • STAS+ tumors: ~2.5× higher recurrence rate after wedge resection vs STAS−
- • STAS+ status is independent of tumor size, visceral pleural invasion, and lymphovascular invasion
- • Current practice: always report STAS in resection specimens; document in MDT decision record
- • Still being incorporated into formal staging — not yet in TNM but in WHO classification
ctDNA (MRD) During Adjuvant Therapy — 2026 Landscape
Molecular Residual Disease (MRD) Monitoring
Circulating tumour DNA (ctDNA) as a Minimal Residual Disease (MRD) biomarker is one of the most rapidly evolving areas in resected NSCLC management (2025–2026 data).
Post-Surgical ctDNA Clearance
ctDNA clearance at 4–6 weeks post-resection is a strong positive prognostic marker. Persistent ctDNA post-surgery (MRD+) predicts high recurrence risk even in radiologically clear patients.
During Adjuvant Osimertinib
In ADAURA, ctDNA clearance after 6 weeks of osimertinib was associated with markedly improved DFS outcomes. Rising ctDNA during adjuvant osimertinib is an early signal of treatment failure — consider restaging and resistance testing before clinical/radiological progression.
Note: ctDNA-guided treatment escalation is not yet a guideline-endorsed standard but is incorporated into multiple clinical trials (2024–2026). Current recommendation: use ctDNA as a prognostic and monitoring tool within clinical trial contexts or tertiary MDT settings.
NeoADAURA — Neoadjuvant Osimertinib for Resectable EGFR NSCLC
NeoADAURA — Phase III Neoadjuvant Osimertinib ± Chemo (2025 Readout)
Design: N=303, resectable Stage IB–IIIB EGFR-mutant NSCLC (Ex19del/L858R), three arms: (A) osimertinib monotherapy × 3 cycles neoadjuvant, (B) osimertinib + platinum-pemetrexed × 3 cycles, (C) chemo alone × 3 cycles.
MPR (≤10% viable tumor): Arm B (osimertinib + chemo): 35% MPR; Arm A (osimertinib mono): 15% MPR; Arm C (chemo): 7% MPR.
pCR: Arm B: 14%, Arm A: 7%, Arm C: 3%.
Nodal downstaging (N2→N0): Significantly better in Arm B — this is the key downstream benefit for resectability and long-term prognosis.
EFS: Immature; long-term follow-up ongoing.
Status (2026): Not yet standard of care — neoadjuvant EGFR TKI is investigational. Adjuvant osimertinib per ADAURA remains the standard post-resection.
NeoADAURA vs ADAURA — Decision Framework
| Feature | ADAURA (Adjuvant, Current Standard) | NeoADAURA (Neoadjuvant, Investigational) |
|---|---|---|
| Timing of osimertinib | Post-surgery (adjuvant) | Pre-surgery (neoadjuvant) ± post-surgery |
| Evidence level | Phase III, FDA approved, OS benefit confirmed | Phase III, pCR/MPR endpoint, EFS immature |
| Guideline status | Standard of care (NCCN cat 1, ESMO) | Investigational only — not yet standard |
| Nodal downstaging | No downstaging (surgery first) | Meaningful downstaging — especially N2→N0 with combination arm |
| Best use case | All resected EGFR IB–IIIA after R0 resection | Clinical trial; bulky resectable EGFR IIIA where downstaging is critical |
Choosing Osimertinib Monotherapy vs Osimertinib + Chemo (Neoadjuvant)
Osimertinib Monotherapy (Arm A)
Lower pCR (7%) but excellent tolerability. Consider for patients who cannot tolerate platinum-based chemotherapy — elderly, poor renal function, neuropathy, hearing loss.
Osimertinib + Chemotherapy (Arm B)
Higher MPR (35%) and pCR (14%). Consider for fit patients where nodal downstaging is critical (borderline resectable N2 disease). Adds platinum toxicity.
Molecular co-mutations favouring combination: TP53 co-mutation, MET amplification, high baseline ctDNA burden.
Biological reason for low pCR in EGFR-mutant disease: EGFR TKIs suppress tumour growth without inducing significant tumour cell death (cytostatic vs cytotoxic). This explains why pCR rates are much lower (~7–14%) than with chemo-IO (~24–25%). However, the shift from pCR to MPR and surgical feasibility defines the rationale for neoadjuvant EGFR TKIs — sustained suppression prevents progression before the surgical window, even without complete eradication.
Nodal Downstaging — Prognostic Weight
Conversion of N2 to N0 (ypN0) after neoadjuvant therapy is one of the strongest independent prognostic markers in resected NSCLC, surpassing pCR in some analyses. Data from CheckMate 816 and NeoADAURA consistently show:
- • N2→N0 conversion: 5-yr OS improvement of ~20–30% absolute vs persistent N2 (yN2)
- • N2→N0 is a valid surgical gateway — MDT discussion warranted for any patient with baseline N2 who achieves ypN0 on restaging PET
- • Persistent yN2: still proceed to surgery if R0 achievable, then maximise adjuvant systemic therapy intensity
Surgery as an Inflammatory Boost for irPneumonitis — Key Safety Signal
Immune-related pneumonitis (irPneumonitis) after neoadjuvant IO followed by surgery:There is a recognised “surgical inflammatory boost” phenomenon in patients who received neoadjuvant checkpoint inhibitors. Surgery itself activates the immune system — in the context of recent IO, this can precipitate or exacerbate immune-related pneumonitis in the perioperative period. Incidence is ~3–5% in pooled neoadjuvant IO surgical series. Management: high-dose corticosteroids (1–2 mg/kg prednisolone equivalent); do not restart IO until Grade 0–1 resolution. Inform anaesthetic and surgical teams pre-operatively if patient received neoadjuvant IO within 8 weeks.
Relevant Clinical Calculators
Clinical decision support tools for early-stage NSCLC — performance status, geriatric assessment, comorbidity scoring, and VTE risk.
Clinical reference only. These guidelines are intended for qualified healthcare professionals. Content reflects NCCN NSCLC 3.2025 and ESMO guidelines 2026. Treatment decisions should be individualised based on patient-specific factors, local protocols, and multidisciplinary team input. Always apply clinical judgment and consult local institutional guidelines where applicable.