Nottingham Prognostic Index (NPI) Calculator
Estimates breast cancer prognostic group from tumour size, nodal status and grade. For use by trained health professionals only.
NPI = (0.2 × tumour size in cm) + node stage + grade- Node stage: 1 = 0 nodes; 2 = 1–3 positive nodes; 3 = ≥4 positive nodes.
- Grade (Nottingham/Elston–Ellis): 1 = grade I; 2 = grade II; 3 = grade III.
- ≤ 3.4 – Good prognosis (low risk)
- > 3.4 to 5.4 – Moderate prognosis (intermediate risk)
- > 5.4 – Poor prognosis (high risk)
Score & Interpretation
Enter tumour size, node status, and grade, then click “Calculate NPI & Prognostic Group” to view the calculated score and prognostic band.
This tool is intended as an educational adjunct for clinicians familiar with breast cancer prognostic indices. It does not provide personalised survival probabilities and must not be used by patients for self-assessment. Always integrate NPI within multidisciplinary discussion, guideline recommendations and shared decision-making.
The Nottingham Prognostic Index (NPI) is a clinicopathological score used to estimate prognosis in early invasive breast cancer after surgery. It combines three key pathological features into a single number, helping to stratify patients into risk groups and guide decisions about adjuvant therapy (e.g. chemotherapy, endocrine therapy). IIAR Journals+4Wikipedia+4archive.datadictionary.nhs.uk+4
NPI was developed in Nottingham in the early 1980s from multivariate analysis showing that tumour size, lymph node status, and tumour grade were the strongest independent predictors of outcome.SpringerLink+1 The formula is:
NPI = (0.2 × tumour size in cm) + lymph node stage + tumour grade
Where:SpringerLink+3Wikipedia+3SpringerLink+3
- Tumour size (S): maximum invasive tumour diameter in centimetres
- Nodal stage (N):
- 1 = no positive axillary nodes
- 2 = 1–3 positive nodes
- 3 = ≥4 positive nodes
- Histological grade (G) (Nottingham/Elston–Ellis grade):
- 1 = well-differentiated (grade I)
- 2 = moderately differentiated (grade II)
- 3 = poorly differentiated (grade III)
The total NPI score typically stratifies patients into three prognostic groups: Frontiers+4SpringerLink+4SpringerLink+4
- ≤ 3.4 – Good prognosis (low risk)
- > 3.4 to 5.4 – Moderate prognosis (intermediate risk)
- > 5.4 – Poor prognosis (high risk)
Higher NPI values are associated with worse long-term survival and a higher risk of recurrence. The score has been widely validated and remains in use, often alongside genomic tests (Oncotype DX, Prosigna, etc.) and newer extensions such as NPI+ or combined nomograms.Frontiers+3Nature+3Oncotarget+3
