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Metastatic Colorectal Cancer Treatment by Biomarker

Before you choose a first-line regimen, you need 5 test results. Do you have all of them?

NCCN CRC 4.2025ESMO Living v1.3 · Jul 2025Last reviewed: Apr 2026

Non-negotiable tests before ANY systemic therapy

Required for all patients

  1. 1MMR/MSI status (dMMR/MSI-H: 3.5–6.5%)
  2. 2KRAS exons 2, 3, 4 + NRAS exons 2, 3, 4 (extended RAS)
  3. 3BRAF V600E (5–12%)
  4. 4Primary tumor sidedness (left vs. right)
  5. 5Resectability assessment

Additional biomarkers in RAS-WT patients

  • HER2 amplification (IHC 3+ or 2+/FISH, 3–5% of RAS-WT)
  • KRAS G12C mutation
  • NTRK fusion
  • RET fusion
  • POLE/POLD1 mutations (2–4% all-stage, <1% mCRC)
  • TMB-H

Tissue is gold standard. ctDNA if tissue unavailable (sensitivity 67%, specificity 96%, concordance 61–93%).

Section 1 — Workup

What tests must be completed before starting any systemic therapy in mCRC?

Colonoscopy & Tissue Acquisition

  • Preoperative colonoscopy: localize tumor, obtain tissue (synchronous invasive CRC 3–5%, synchronous adenomas ~30%)
  • If incomplete: CT colonography (preferred), MRI colonography, or barium enema (less preferred)
  • If not feasible pre-op: completion colonoscopy post-resection

Imaging

  • Initial staging: contrast CT chest/abdomen/pelvis
  • Liver MRI: when CT findings equivocal, or liver mets appear potentially resectable (better sensitivity for small lesions, assessing number/size/vasculature relationship)
  • FDG-PET useful for: rising CEA without visible metastatic disease, clarifying disease extent for metastasectomy planning, may avoid non-therapeutic laparotomy

Biomarkers & Labs

  • Baseline CEA: obtain pre-treatment; persistent post-operative elevation suggests residual disease or metastasis (not for screening — low sensitivity/specificity for early-stage)
  • DPD deficiency testing prior to 5-FU-based chemotherapy
  • UGT1A1*28: affects irinotecan metabolism → dose adjustment may be needed (some NGS panels include this)

Family History & Lynch Screening

Collect 3-generation pedigree; at minimum 1st and 2nd degree relatives. Inquire about CRC, endometrial, ovarian, gastric, small bowel, renal pelvis/ureter — may identify Lynch syndrome.

Section 2 — Resectability Assessment

Are the metastases resectable? This single question changes the entire treatment goal.

Resectability Criteria

  • Limited number and location of mets
  • Adequate remnant organ function
  • Good performance status
  • Absence of prohibitive comorbidities

Survival Outcomes

  • 5+ year survival possible in selected cases
  • ~50% survival with metastasectomy
  • Cure rare (~20–30%) even after complete resection
  • Most patients have recurrence

Sites

  • Most feasible for liver and lung mets
  • Controlled/resectable primary tumor required
  • Peritoneal limited to specialized centers
  • Oligometastatic (≤5 lesions, ≤2 organs)

Timing of Surgery in Synchronous Metastatic Disease

No universal consensus — individualize based on symptoms, tumor burden, and institutional expertise.

Standard sequence

Primary resection first → systemic therapy → metastasectomy

Liver-first strategy

Reverse strategy: address liver mets before primary in select cases

Simultaneous resection

Primary and metastases resected in same operation (selected centers)

Perioperative Chemotherapy

When perioperative chemo may NOT be needed

  • Good PS, resectable disease with favorable biology, high chance of R0 resection
  • e.g. upfront surgery for initially resectable, low-risk liver-only met (≤4 lesions, all in one lobe, RAS/BRAF-WT)
  • Avoids oxaliplatin/irinotecan hepatotoxicity; no OS benefit shown with perioperative chemo in this setting

Preferred perioperative regimens

  • Oxaliplatin-based (FOLFOX or XELOX) — preferred
  • FOLFOXIRI for young fit patients
  • FOLFIRI if received adjuvant FOLFOX within past 12 months
  • Left-sided RAS-WT: add cetuximab or panitumumab for conversion therapy

Pre-op chemo duration limits

Limit pre-op chemo to ≤4 cycles (~16 weeks); imaging every 6–8 weeks.

Extended chemo (>16 weeks): no improvement in pathologic response + increases chemo-related liver injury (oxaliplatin → sinusoidal injury; irinotecan → steatosis/steatohepatitis).

Delay resection ≥4 weeks post-chemo; ≥6 weeks if bevacizumab used.

Postoperative Management

  • No prior chemo → adjuvant FOLFOX or XELOX; avoid irinotecan-containing regimens
  • Neoadjuvant chemo given → complete full 6-month course inclusive of pre-op cycles; do not repeat FOLFOX if received within prior 12 months

Section 3 — Systemic Therapy Principles

Doublet or triplet? Bev or anti-EGFR? How fit is the patient for intensive therapy?

Treatment Goals

  • Potentially resectable: maximal tumor shrinkage → curative surgery
  • Unresectable: palliation (prolong survival, maintain QOL)
  • Early initiation preferred; defer only for minimal burden, slow tempo, or patient preference

Chemotherapy Backbone

  • 5-FU/capecitabine, oxaliplatin, irinotecan
  • 1L efficacy: FOLFOX = FOLFIRI = XELOX
  • SOX = FOLFOX = XELOX in Asian populations
  • XELIRI not recommended in the US (higher toxicity, especially diarrhea)

Targeted Agents

Anti-EGFR

Cetuximab, panitumumab

RAS/BRAF-WT ONLY

Anti-VEGF

Bevacizumab, ramucirumab, aflibercept

All molecular subgroups

KRAS G12C inhibitors

Adagrasib, sotorasib (+ anti-EGFR)

KRAS G12C mutation

HER2-targeted

Trastuzumab+tucatinib, T-DXd, trastuzumab+pertuzumab/lapatinib

HER2-amplified

NTRK inhibitors

Larotrectinib, entrectinib, repotrectinib

NTRK fusion

Immunotherapy

Pembrolizumab, nivolumab ± ipilimumab

dMMR/MSI-H ONLY

Triplet vs Doublet Chemotherapy — When to escalate

Indications for FOLFOXIRI + bevacizumab

  • • Good PS, high tumor burden, or initially unresectable liver mets needing conversion therapy
  • • Duration: 3–4 months, then transition to non-oxaliplatin maintenance (5-FU + bev)

Meta-analysis evidence (TRIBE, TRIBE2, CHARTA, OLIVIA, STEAM): FOLFOXIRI+bev → better PFS, OS, and RR at expense of higher toxicity.

Triplet + anti-EGFR — NOT recommended

TRIPLETE trial: FOLFOXIRI+panitumumab vs FOLFOX+panitumumab → ORR not improved, more toxic, no added benefit.

Oxaliplatin & Irinotecan Management Strategies

Oxaliplatin

  • • Stop at 3–4 months to avoid cumulative neuropathy
  • • Continue 5-FU or capecitabine ± targeted as maintenance
  • • OPTIMOX-1: "stop and go" supported
  • • OPTIMOX-2: maintenance better than complete stop for PFS and OS

Irinotecan

  • • Continue as long as response and tolerance persist
  • • Intermittent schedules (2 months on/off) may be considered with comparable PFS and OS
  • • No cumulative dose-limiting toxicity like oxaliplatin neuropathy

Complete treatment break

Valid after CR or PR — appropriate for small-volume disease, symptom-free patients, patient preference. Monitor every 2 months, restart at progression.

Section 4 — First-Line Therapy by Biomarker

Which biomarker subgroup is this patient? This is the core branching decision.

Molecular subgroups — select 1L pathway

dMMR/MSI-H

3.5–6.5%

BRAF V600E

5–12%

RAS/BRAF-WT Left

~25%

RAS/BRAF-WT Right

~15%

RAS-mutant

~50%

KRAS G12C

3–4%

HER2-amplified

3–5% RAS-WT

POLE/POLD1

<1%

4a. dMMR/MSI-H

3.5–6.5% of mCRC
CheckMate 8HW — Nivolumab + Ipilimumab (preferred 1L)

ORR 71% vs 38% vs 35% (nivo+ipi vs nivo vs chemo)

PFS NR vs 40 months vs 6 months; superior OS vs chemotherapy

Preferred option for dMMR/MSI-H — combination recommended over monotherapy

CheckMate 8HW — Nivolumab monotherapy

ORR 58%, PFS 40 months

Lower PFS/ORR vs combo; use if toxicity concerns or ipilimumab contraindicated

KEYNOTE-177 — Pembrolizumab vs chemotherapy

OS 78 vs 37 months, PFS 17 vs 8 months, ORR 46% vs 33%

Durable responses and favorable toxicity over chemotherapy

ICI Duration Guidance

  • • No universal standard; expert recommendation: minimum 12 months, maximum 2 years
  • • CR confirmed on ≥2 scans → may stop at 1 year
  • • PR/SD → continue up to 2 years if tolerated
  • • Retrospective data: no OS difference between fixed 2 years vs >2 years

Resectable dMMR: Despite ICI efficacy, recommend chemotherapy upfront if resectable; immunotherapy still being explored in this setting.

4b. BRAF V600E

5–12% of mCRC
BREAKWATER — Encorafenib + cetuximab + FOLFOX (preferred 1L BRAF V600E)

OS 30 vs 15 months; PFS 13 vs 7 months; ORR 60% vs 37% vs SOC

Standard of care when targeted therapy available

If targeted therapy unavailable: FOLFOXIRI+bev (triplet-suitable patients) or FOLFOX+bev

Critical: BRAF V600E + dMMR co-mutation

BRAF V600E often co-occurs with sporadic dMMR (MLH1 methylation). If dMMR co-mutation present, immunotherapy is preferred over targeted therapy.

Dabrafenib+trametinib in mCRC

Though FDA tumor-agnostic approval exists, the approval trial excluded mCRC. NOT recommended in patients who progress on encorafenib+cetuximab.

4c. RAS/BRAF-WT — Left-sided Primary

Anti-EGFR preferred
  • Anti-EGFR (cetuximab or panitumumab) + doublet chemotherapy = standard of care
  • Primary tumor sidedness is both prognostic and predictive
  • Anti-EGFR should only be used in extended RAS-WT tumors (KRAS + NRAS exons 2, 3, 4)
  • Triplet + anti-EGFR NOT routinely recommended (TRIPLETE trial: no benefit, more toxic)

4d. RAS/BRAF-WT — Right-sided Primary

Bevacizumab preferred
  • Bevacizumab-based therapy preferred (doublet or triplet)
  • Anti-EGFR has no role in right-sided 1L and may be harmful if used without specific cytoreduction intent
  • Triplet (FOLFOXIRI+bev) for high tumor burden or conversion intent

4e. RAS-mutant (KRAS or NRAS)

~50% of mCRC
  • Doublet or triplet chemo ± bevacizumab
  • Avoid anti-EGFR (cetuximab, panitumumab) — no benefit, potential harm
  • Triplet only in selected fit patients (high tumor burden, conversion intent)
  • Right-sided and/or RAS-mutant for conversion: FOLFOXIRI+bev preferred

4f. KRAS G12C mutation

3–4% of mCRC
KRYSTAL-1 — Adagrasib + cetuximab (Phase 1/2)

ORR 34%, PFS 7 months, OS 16 months

Landmark response rates in a historically difficult-to-treat subgroup

CodeBreak 300 — Sotorasib + panitumumab (Phase 3)

ORR 26% vs 0%, PFS 6 vs 2 months vs lonsurf/regorafenib

Line of therapy considerations

More often used in 2L/3L after prior oxaliplatin AND irinotecan exposure. Formal 3L+ indication requires prior 5-FU/capecitabine, oxaliplatin, AND irinotecan treatment.

4g. HER2-amplified

3–5% of RAS-WT
  • HER2 amplification: IHC 3+ or 2+/FISH confirmation required
  • 1L: Trastuzumab + tucatinib + FOLFOX (MOUNTAINEER-03 ongoing — no efficacy results published yet)
  • For established options in later lines, see Section 8 (3L+)

4h. POLE/POLD1 mutation

<1% of mCRC

Key features

  • • Rare <1% of mCRC but highly immunogenic
  • • Associated with ultramutated phenotype (TMB >100 mut/Mb)
  • • POLE mutations more common in pMMR/MSS tumors
  • • POLD1 mutations more common in dMMR/MSI-H

TMB >50 mut/Mb → ICI strategy

Treat like dMMR/MSI-H: nivo+ipi preferred; monotherapy options: pembrolizumab, nivolumab. Retrospective data suggests superior outcomes vs dMMR/MSI-H on ICI.

TMB <50 mut/Mb → pMMR/MSS strategy

Follow standard pMMR/MSS strategy: chemo ± targeted. TMB level (not MSI/MMR status alone) guides ICI use.

Note: No RCTs available; management relies on retrospective studies, expert consensus, and real-world outcomes.

Section 5 — Maintenance Therapy

Oxaliplatin is done at 3–4 months — what do you maintain with?

Scenario

After oxaliplatin + bevacizumab

Strategy

De-escalate to fluoropyrimidine + bevacizumab

Scenario

After oxaliplatin + anti-EGFR

Strategy

De-escalate to fluoropyrimidine + anti-EGFR

Scenario

After FOLFIRI or XELIRI

Strategy

Continue full regimen (no cumulative toxicity concerns)

Scenario

Disease progression on maintenance

Strategy

Reintroduce initial therapy if previously effective

OPTIMOX-1: Supports "stop and go" oxaliplatin strategy — stopping oxaliplatin while maintaining fluoropyrimidine is non-inferior.
OPTIMOX-2: Maintenance therapy is better than complete chemotherapy discontinuation for PFS and OS.

Section 6 — Conversion to Resectability

The mets responded — is resection now possible? How do you reassess?

Imaging frequency

Every 6–8 weeks during induction chemotherapy

Surgery timing

As soon as metastases become clearly resectable — do not over-treat

Chemo limit

≤16 weeks; extended chemo does not improve pathologic response

Resection after poor response to 1L

  • • Do NOT deny metastasectomy/ablation solely because of poor response to chemotherapy
  • • Patients still benefit from 2L followed by resection
  • • Intra-arterial chemotherapy as rescue tool for liver-dominant disease

Oligometastatic Disease (OMD)

Definition: ≤5 metastatic lesions, limited sites (liver, lung, peritoneum); synchronous or metachronous.

  • • Start systemic therapy in all patients to test tumor biology and downstage (ESMO recommendation)
  • • Responded disease → proceed with local treatment
  • • Oligoprogressive disease → local treatment to progressive lesions, continue same systemic therapy

Local Therapy Options

ModalityIndicationKey Criteria
SurgeryCurative-intent resectable OMD≤5 lesions, ≤2 organs, R0 feasible, good PS
Thermal ablation (RFA/MWA)Small deep liver mets, surgery unfit≤3cm, ≤3–5 lesions, ≥1cm from major bile ducts
SBRTNot suitable for surgery/ablation≤5 lesions, ≤5cm, well-defined target
HAIC / TARE/SIRT Y-90Chemorefractory liver-only or oligoprogressionPreserved liver function, patent vessels, no extrahepatic shunting
TACEChemorefractory liver-only, not Y-90/HAIC candidatePreserved liver function, patent portal vein

Isolated peritoneal metastases

Offer complete cytoreduction surgery where feasible. HIPEC considered experimental — should only be used in clinical trials; no consensus or OS benefit shown outside studies.

Section 7 — Second-Line Therapy by Biomarker

What changed at progression? Which biomarker drives second-line choice?

Second-line therapy is determined by prior exposure and molecular profile. Key principle: switch chemotherapy backbone (oxaliplatin → irinotecan or vice versa) and reassess targeted agent eligibility.

RAS-WT and anti-EGFR naïve at 2L

Left-sided

Anti-EGFR (cetuximab/panitumumab) ± chemotherapy

Right-sided

Anti-angiogenic + chemotherapy preferred

BRAF V600E — 2L (BEACON trial)

BEACON — Encorafenib + cetuximab ± binimetinib (≥1 prior line)

Triplet vs doublet vs SOC: OS 9 vs 9 vs 5.4 months; ORR 26% vs 20% vs 2%

FDA approved doublet (encorafenib + cetuximab) only

Triplet considered in highly symptomatic/bulky disease — no OS advantage over doublet, higher toxicity

Note: Dabrafenib+trametinib has tumor-agnostic FDA approval but was excluded from mCRC in the approval trial — not recommended after encorafenib+cetuximab failure.

dMMR/MSI-H and IO naïve at 2L

CheckMate 142 — Nivolumab + ipilimumab

ORR 65%, 4yr PFS 53%, 4yr OS 71%

CheckMate 142 — Nivolumab monotherapy

ORR 31%, 4yr PFS 36%, 4yr OS 49%

KEYNOTE-164 — Pembrolizumab

1+ prior line: ORR 35%, PFS 4 months, OS 47 months

2+ prior lines: ORR 33%, PFS 2 months, OS 31 months

GARNET — Dostarlimab

ORR 44%, PFS 8 months, OS not reached

KRAS G12C — 2L/3L (after prior oxaliplatin AND irinotecan)

KRYSTAL-1 — Adagrasib + cetuximab

ORR 34%, PFS 7 months, OS 16 months

CodeBreak 300 — Sotorasib + panitumumab (Phase 3)

ORR 26% vs 0%, PFS 6 vs 2 months vs lonsurf/regorafenib

RET fusions — Pan-tumor, any line

Libretto-001 — Selpercatinib (mCRC subgroup)

ORR 20%, DOR 9 months

Other RET inhibitors (pralsetinib) under investigation

NTRK fusions — Pan-tumor, any line

Larotrectinib — mCRC subgroup

ORR 50%, DOR 4 months

Entrectinib — mCRC subgroup

ORR 20%, DOR 18 months; better CNS penetration

Repotrectinib — at TRK resistance

Active against TRK resistance mutations; ORR 33%, DOR 18 months

TMB-H (≥10 mut/Mb) — Pan-tumor

KEYNOTE-158 — Pembrolizumab (pan-tumor)

ORR 29% — NOTE: no mCRC patients included; approval extrapolated to CRC

TMB-H + pMMR/MSS without POLE/POLD1: Do NOT routinely offer immunotherapy. Consider only if no other systemic options exist, with informed patient consent.

Other 2L Options (by prior exposure)

  • Switch chemotherapy backbone: oxaliplatin → irinotecan (or vice versa)
  • Add anti-angiogenic: bevacizumab, aflibercept (VELOUR trial), ramucirumab (RAISE trial)
  • Bevacizumab continuation beyond PD or reintroduction (ML18147/TML, BEBYP trials)
Clinical Calculators

Section 8 — Third-Line and Beyond

What are the options after two lines of therapy?

RAS-WT + BRAF-WT

SUNLIGHT — Lonsurf + bevacizumab (PREFERRED)

vs lonsurf alone: PFS 6 vs 2 months, OS 11 vs 8 months

Now preferred over lonsurf monotherapy in eligible patients

RESOURCE — Lonsurf monotherapy

vs placebo: OS 7 vs 5 months

CORRECT — Regorafenib vs placebo

PFS 1.9 vs 1.7 months, OS 6.4 vs 5 months

CONCUR (Asia) — Regorafenib

PFS 3.2 vs 1.7 months, OS 8.8 vs 6.3 months

ReDOS — Regorafenib dose-escalation strategy

Weekly dose escalation (80→120→160mg) improved tolerability and OS 9.8 vs 6 months

Start at 80mg, escalate weekly — preferred dosing strategy

FRESCO (China) + FRESCO-2 (international) — Fruquintinib

FRESCO: PFS 3.7 vs 1.8 months, OS 9.3 vs 6.6 months

FRESCO-2: PFS 3.7 vs 1.8 months, OS 7.4 vs 4.8 months

VELO — EGFR rechallenge: panitumumab + lonsurf

vs lonsurf alone: PFS 4 vs 2.5 months, OS 13 vs 12 months

Appropriate after multiple intervening lines (RAS-WT clones re-emerge)

Also consider: single-agent anti-EGFR (if not previously used), irinotecan + cetuximab (if not previously used)

RAS-WT + BRAF-WT + HER2-amplified

MOUNTAINEER — Trastuzumab + tucatinib (≥2 prior lines)

ORR 38%, PFS 8 months, OS 24 months

DESTINY-CRC01 — T-DXd (Enhertu)

ORR 45%, PFS 7 months, OS 16 months

Reserved for later lines after trastuzumab+chemo failure

DESTINY-CRC02 — T-DXd dose comparison

5.4mg/kg vs 6.4mg/kg: similar ORR/PFS, lower ILD risk at 5.4mg/kg → use 5.4mg/kg

Off-label options: Trastuzumab+lapatinib (HERACLES), trastuzumab+pertuzumab (MyPathway, TAPUR)

RAS-mutant

  • Lonsurf + bevacizumab (preferred), lonsurf monotherapy, regorafenib, fruquintinib
  • KRAS G12C: adagrasib + cetuximab, sotorasib + panitumumab

RAS-mutant + HER2-amplified (rare co-occurrence)

Co-occurrence is rare.

Do NOT use HER2-targeted therapy in RAS-mutant tumors outside clinical trials — no demonstrated benefit.

SOC: chemo doublets/triplets ± bevacizumab.

BRAF V600E

  • Encorafenib + cetuximab (BEACON) — if not used in 1L
  • Lonsurf + bevacizumab, lonsurf monotherapy, regorafenib, fruquintinib

Section 9 — Special Populations

Elderly, frail, peritoneal-only, oligometastatic — how do you adapt?

Elderly / Frail Patients

  • Use G8, CARG, ECOG, CCI to assess fitness before starting therapy
  • Dose-reduce oxaliplatin first when de-escalating
  • Consider fluoropyrimidine monotherapy if doublet not tolerated
  • Capecitabine preferred over infusional 5-FU (no port, fewer hospital visits)
  • Avoid triplet (FOLFOXIRI) in frail patients

Poor Performance Status (ECOG 3–4)

  • Best supportive care should always be discussed
  • If PS is clearly performance-status related to disease (not comorbidity), a short trial of less intensive therapy may be justified
  • Reassess PS after 4–8 weeks; discontinue if no improvement
  • Avoid aggressive chemotherapy in truly frail patients

Peritoneal-only Disease

  • Complete cytoreduction surgery + HIPEC (investigational only — clinical trial setting)
  • Systemic therapy for disease control outside surgical candidates
  • Survival significantly worse than liver/lung-only mCRC
  • HIPEC should ONLY be offered within clinical trials — no OS benefit shown outside studies

Oligometastatic Disease

  • Covered in detail in Section 6 (Conversion to Resectability)
  • Key principle: systemic therapy first to test tumor biology, then local treatment if response
  • Oligoprogressive disease: local treatment to progressive lesions, continue same systemic therapy

Synchronous Liver Metastases

  • Simultaneous vs staged resection — no universal standard
  • Individualize based on tumor burden, symptoms, and institutional expertise
  • Liver-first strategy for liver-dominant, borderline-symptomatic primary
  • Consider perioperative chemotherapy to assess tumor biology before committing to surgery

Section 10 — Clinical FAQs

Does sidedness matter if the patient has RAS mutation?

In RAS-mutant disease, sidedness does NOT change treatment — anti-EGFR is contraindicated regardless of tumor location. Sidedness matters primarily in RAS/BRAF-WT disease for the anti-EGFR vs bevacizumab decision.

When should I use FOLFOXIRI vs FOLFOX in 1L?

FOLFOXIRI + bevacizumab is indicated for good PS (ECOG 0–1), high tumor burden, or conversion intent for initially unresectable liver mets. Duration 3–4 months then transition to maintenance with 5-FU + bev. Triplet + anti-EGFR is not recommended (TRIPLETE trial: no added benefit, more toxic).

How long do you continue immunotherapy in dMMR mCRC?

No universal standard. Expert recommendation: minimum 12 months, maximum 2 years. CR confirmed on ≥2 scans → may stop at 1 year. Retrospective data shows no OS difference between fixed 2 years vs longer duration. PR/SD → continue up to 2 years if tolerated.

What is the EGFR rechallenge concept?

After progression on anti-EGFR therapy, RAS-WT clones may re-emerge and restore anti-EGFR sensitivity. The VELO trial demonstrated panitumumab + lonsurf vs lonsurf alone → PFS 4 vs 2.5 months. Most appropriate after multiple intervening lines where EGFR-resistant clones have been diluted.

Can I use bevacizumab beyond progression?

Yes. ML18147/TML and BEBYP trials both support bevacizumab continuation beyond first progression in combination with a new chemotherapy backbone. Reintroduction of bev after a treatment break is also valid.

What is the role of ctDNA in mCRC?

Tissue biopsy remains the gold standard for molecular profiling. ctDNA (liquid biopsy) is useful when tissue is unavailable or insufficient (sensitivity 67%, specificity 96%). The discordance rate between primary and recurrent tumor genotyping is ~20% — retesting at progression (especially for RAS status) is clinically relevant.

When is HIPEC indicated for peritoneal mets?

HIPEC remains experimental in mCRC and should only be offered within clinical trials. No OS benefit has been demonstrated outside of study settings. Complete cytoreduction to no visible residual disease is the primary goal of any peritoneal surgery.

What if a patient has both BRAF V600E and dMMR?

dMMR frequently co-occurs with BRAF V600E mutation (through sporadic MLH1 promoter methylation, not Lynch syndrome). In this setting, immunotherapy is preferred over BRAF-targeted therapy. Use ICI in 1L rather than encorafenib + cetuximab + FOLFOX.

Medical Disclaimer

These guidelines are intended for qualified healthcare professionals as a clinical reference tool. Always apply individual clinical judgment and consider patient-specific factors. Content reflects NCCN CRC 4.2025 and ESMO Living Guideline v1.3 (Jul 2025). This is not a substitute for formal medical education, professional training, or individualized clinical decision-making.