Predictive Value of Tumor Ki-67 Expression in Two Randomized Trials of Adjuvant Chemoendocrine Therapy for Node-Negative Breast Cancer

Viale, Giuseppe ; Regan, Meredith M. ; Mastropasqua, Mauro G. ; Maffini, Fausto ; Maiorano, Eugenio ; Colleoni, Marco ; Price, Karen N. ; Golouh, Rastko ; Perin, Tiziana ; Brown, R. W. ; Kovács, Anikó ; Pillay, Komala ; Öhlschlegel, Christian ; Gusterson, Barry A. ; Castiglione-Gertsch, Monica ; Gelber, Richard D. ; Goldhirsch, Aron ; Coates, Alan S.

In: Journal of the National Cancer Institute, 2008, vol. 100, no. 3, p. 207-212

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    Summary
    Several small studies have reported that having a high percentage of breast tumor cells that express the proliferation antigen Ki-67 (ie, a high Ki-67 labeling index) predicts better response to neoadjuvant chemotherapy. However, the predictive value of a high Ki-67 labeling index for response to adjuvant chemotherapy is unclear. To investigate whether Ki-67 labeling index predicts response to adjuvant chemoendocrine therapy, we assessed Ki-67 expression in tumor tissue from 1924 (70%) of 2732 patients who were enrolled in two randomized International Breast Cancer Study Group trials of adjuvant chemoendocrine therapy vs endocrine therapy alone for node-negative breast cancer. A high Ki-67 labeling index was associated with other factors that predict poor prognosis. Among the 1521 patients with endocrine-responsive tumors, a high Ki-67 labeling index was associated with worse disease-free survival but the Ki-67 labeling index did not predict the relative efficacy of chemoendocrine therapy compared with endocrine therapy alone. Thus, Ki-67 labeling index was an independent prognostic factor but was not predictive of better response to adjuvant chemotherapy in these studies