Benefit from adjuvant taxanes and endocrine responsiveness in breast cancer.

Several phase III trials have been coincident in showing a benefit with adjuvant taxanes in node-positive breast cancer (BC). These trials provide level I evidence of the efficacy of these drugs. The absolute 5-year DFS gain obtained with the taxane-containing regimens in the positive studies ranged from 4% to 7%. However, the regimens including taxanes are more toxic than the conventional anthracyline-containing combinations. Therefore, the pre-treatment identification of the small proportion of patients who actually benefit from taxanes is of major importance. Several attempts have been made to identify the biological peculiarities of the BC patients who benefit most with taxanes, largely based on retrospective subset analyses. Hormone receptor (HR) status, one of the critical determinants of BC biology, had been suggested to be a factor modulating response to adjuvant chemotherapy in general and taxanes in particular. Unfortunately, none of the first-generation adjuvant taxane trials was designed to address the question of the differential efficacy of taxanes in the specific subgroups of HR positive and HR negative BC patients. Indirect (retrospective, unplanned) analysis suggest that the magnitude of benefit from taxanes is somewhat more in the HR negative subset, but the benefit also exists, and is clinically relevant, in patients with HR positive cancers. Therefore, the predictive value of HR status in the selection of patients for adjuvant taxane therapy is low. The predictive value of HER2 status in addition to HR status to select patients for the same purpose remains controversial.