THE IMPORTANT PROGNOSTIC VALUE OF KI-67 EXPRESSION AS DETERMINED BY IMAGE-ANALYSIS IN BREAST-CANCER

A series of 191 female breast carcinomas (with long-term follow-up) we re analysed immunohistochemically (with a monoclonal MIB1 antibody) fo r Ki-67 (a proliferation marker) expression with special reference to well-established prognostic factors and patient survival. Expression o f Ki-67 was directly related to the S-phase fraction (P <0.0001), the volume-corrected mitotic index (P <0.0001), histological grade (P <0.0 001), the apoptotic index (P <0.0001), oestrogen and progesterose rece ptor content (P <0.0001 for both) and p53 accumulation (P=0.001). No c orrelation was found between Ki-67 expression and lymph node status (P =0.25), metastasis at operation (n=0.81) or tumour size (n=0.38). The proliferation rate, as measured by image analysis of Ki-67 expression; predicted survival in the entire cohort (P=0.001) and in axillary-lym ph-node-negative (ANN) patients (P=0.003). The difference in recurrenc e-free survival between the high- and low-expression groups was greate st in ANN tumours, 40% (P=0.008). In axillary-lymph-node-positive tumo urs, the Ki-67 expression was not significantly related to recurrence- free survival (P=0.723). The results of multivariate survival analysis showed that tumour size, axillary lymph node status, and mitotic inde x were independent prognostic factors in the entire series whereas, in ANN cases, tumour size and Ki-67 labelling were independent prognosti c factors. These findings imply that Ki-67 expression could be an impo rtant prognostic determinant in breast cancer. Because of the evident loss of the predictive power of tumour size in the 1990s, the prognost ic value of Ki-67 expression may even be accentuated in the currently diagnosed small breast carcinomas.