Prognostic factors in breast cancer: the predictive value of the Nottingham Prognostic Index in patients with a long-term follow-up that were treated in a single institution.

The Nottingham Prognostic Index (NPI) is an index, derived from a retrospective multivariate study, that is able to predict survival in patients with breast cancer. The index is based on tumour size, lymph node stage and histological grade and allows the stratification of patients into three different prognostic groups. The aim of this study was to verify, according to our experience with a long-term follow-up, the effect of some prognostic variables on survival and to establish the independent influence of each of them by means of a survival regression analysis. Then we applied the NPI to the same group of patients in order to assess the predictive power and reproducibility of the index. 402 patients treated from January 1979 to December 1987 were evaluated. In multivariate analysis (Cox proportional hazard model), only size, lymph node involvement and histological grade remained independent prognostic factors. The survival curves obtained after applying the NPI are similar to those for the factors with independent prognostic significance derived from our multivariate analysis. Our improved survival rates may be attributed to the administration of adjuvant therapies to a larger number of patients. The NPI allow us to accurately predict prognosis and we advocate its more common use.