Nottingham Prognostic Index

The Nottingham prognostic index (NPI) is used to determine prognosis following surgery for breast cancer. Its value is calculated using three pathological criteria: the size of the tumour; the number of involved lymph nodes; and the grade of the tumour. It is calculated to select patients for adjuvant treatment.

Calculation
The index is calculated using the formula:


 * NPI = [0.2 x S] + N + G

Where:


 * S is the size of the index lesion in centimetres
 * N is the node status: 0 nodes = 1, 1-3 nodes = 2, >3 nodes = 3
 * G is the grade of tumour: Grade I =1, Grade II =2, Grade III =3