Proliferation index as a prognostic marker in breast cancer

The proliferative activity of tumors has been extensively investigated with different approaches, among which the use of the monoclonal antibody Ki-67 represents an easy and reliable means of assessing cell proliferation. In this study, the proliferative activity of 129 primary breast cancers was investigated, and the results were related to prognosis.

Tumor samples, obtained from 129 patients who underwent surgery between January 1987 and December 1988, were processed for staining by an immunohistochemical procedure (avidin-biotin complex). The median time of observation was 42 months (range, 31-55 months). Life-table analysis (Mantel-Cox) was used to assess the probability of disease-free survival (DFS) and overall survival (OS).

Tumors with high Ki-67 proliferation indices (> 20%) were associated with a higher 4-year probability of relapse of disease (55.3% versus 79.1%; P = 0.003) and death (71% versus 95.6%; P = 0.00005) when compared with tumors with low Ki-67 values. In addition, this proliferative parameter maintained its prognostic significance when the patients were stratified according to lymph node involvement, menopausal status, and nuclear estrogen receptor content.

Tumor proliferative activity as evaluated by the monoclonal antibody Ki-67 seems to be an effective indicator of prognosis in breast cancer for DFS and OS.