Relationship between tumour shrinkage and reduction in Ki67 expression after primary chemotherapy in human breast cancer

The association between tumour shrinkage and reduction in kinetic cell acti vity after primary chemotherapy in human breast cancer is still a matter of investigation. 157 patients with T2-4, N0-1, MO breast cancer received pri mary chemotherapy consisting of either the CMF regimen + tamoxifen (the fir st consecutive 76 cases) or the single agent epirubicin (the subsequent 81) . Ki67, p53, bc12, c-erbB2 and steroid hormone receptors were evaluated imm unohistochemically in tumour specimens obtained before chemotherapy and at surgery. Tumour shrinkage of > 50% occurred in 72.4% of patients. Ki67 expr ession significantly decreased after chemotherapy; the reduction correlated with tumour response in both univariate (P < 0.005) and multivariate analy sis (P = 0.02). p53, bcl-2, steroid hormone receptor and c-erbB2 immunostai ning were scarcely affected. Baseline bcl2 (P = 0.04) and c-erbB2 (P = 0.02 ) were directly and inversely associated with the reduction in Ki67 immunos taining, respectively. Baseline p53 expression (P < 0.01) was directly rela ted with Ki67 expression at residual tumour, whereas oestrogen receptor exp ression (P < 0.001) was inversely related. Ki67 at residual tumour was a be tter predictor for relapse-free survival (RFS) than baseline Ki67. Clinical response (P < 0.03), but not reduction in Ki67, was a significant independ ent predictor for disease recurrence. Chemotherapy was found to induce tumo ur shrinkage and to reduce the number of cells in the cell cycle, but its e ffect on tumour biology/aggressiveness was minimal. Reduction in Ki67 immun ostaining correlated with clinical response but failed to be related to RFS . Ki67 expression at surgery rather than at baseline appears to be a better predictor for disease relapse. (C) 2001 Cancer Research Campaign.