West Midlands Breast Screening Programme

Nottingham Prognostic Index (NPI)

Haybittle et al. (Br J Cancer 1982; 45: 361 – 366, PMID: 7073932) devised the Nottingham Prognostic Index (NPI) as an indicator of breast cancer outcome based on a nodal score, modified Bloom & Richardson grade and invasive size.

NPI score is calculated using the following formula:

NPI Score = (0.2 x Invasive Size) + Grade + Nodes

where

Invasive size is measured in cm
Grade is the modified Bloom & Richardson grade
Nodes = 1 for no positive nodes, 2 for 1, 2 or 3 positive nodes, or 3 for ≥4 positive nodes

The NPI score is converted to a prognostic group:

NPI Score	Prognostic Group
≤2.4	Excellent Prognostic Group (EPG)
2.4 – 3.4	Good Prognostic Group (GPG)
3.4 – 4.4	Moderate Prognostic Group 1 (MPG1)
4.4 – 5.4	Moderate Prognostic Group 2 (MPG2)
>5.4	Poor Prognostic Group (PPG)

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