Original Nottingham Prognostic Index, three-group model (NPI-3)
A source-locked guide to the 1982 postoperative pathology index and its three historical prognostic groups.
Model identity
This route implements the original Nottingham Prognostic Index three-group model, derived by Haybittle and colleagues in 1982 for women with primary operable breast cancer. It combines the largest invasive tumor diameter in centimeters, positive axillary-node count, and Nottingham histologic grade.
NPI = 0.2 x invasive diameter (cm) + node stage + Nottingham grade
Node stage is 1 for zero positive nodes, 2 for one to three, and 3 for four or more.
| Raw NPI | Historical NPI-3 group |
| --- | --- |
| <=3.4 | Good prognostic group |
| >3.4 and <=5.4 | Moderate prognostic group |
| >5.4 | Poor prognostic group |
The raw score is classified without rounding. Display formatting cannot change a group.
Appropriate inputs
The source-locked calculator requires an adult woman with primary operable invasive nonmetastatic breast carcinoma, complete postoperative pathology, and a pretreatment prognostic assessment. Use the largest invasive diameter, the raw count of pathologically positive axillary nodes, and the pathologist-assigned Nottingham grade.
Pure DCIS, recurrent or metastatic/inoperable disease, imaging-only measurements, unevaluated axillary nodes, non-Nottingham grading, unsupported source populations, and post-neoadjuvant measurements are outside this implementation.
Interpretation boundary
The output is a historical NPI-3 group. It does not replace TNM stage, receptor testing, genomic assays, or individualized multidisciplinary assessment. It does not calculate an individual survival or recurrence probability, chemotherapy benefit, treatment response, or treatment recommendation. NPI(6), four-group variants, NPI+, and genomic classifications are separate models.
Later publications reported outcomes for different cohorts and expanded grouping systems. Those data are not automatically transferable to an individual and are deliberately not emitted by this calculator.
Sources
- Haybittle JL, Blamey RW, Elston CW, et al. A prognostic index in primary breast cancer. Br J Cancer. 1982;45:361-366. Full text.
- Todd JH, Dowle C, Williams MR, et al. Confirmation of a prognostic index in primary breast cancer. Br J Cancer. 1987;56:489-492. Full text.
- Galea MH, Blamey RW, Elston CE, Ellis IO. The Nottingham Prognostic Index in primary breast cancer. Breast Cancer Res Treat. 1992;22:207-219. DOI.
Open the source-locked calculator
Enter complete postoperative pathology variables to obtain the original NPI-3 historical group and calculation trace.
Open NPI-3 calculator
Implementation note: OncoToolkit independently verifies the software implementation against the cited model. This is not prospective or independent clinical validation of the NPI itself.