HER2 expression and efficacy of dose-dense anthracycline-containing adjuvant chemotherapy in breast cancer patients

No data are available on the role of HER2 overexpression in predicting the efficacy of dose-dense anthracycline-containing adjuvant chemotherapy in breast cancer patients. We retrospectively evaluated this role in patients enrolled in a phase III study comparing standard FEC21 (5-fluorouracil, epirubicin, and cyclophosphamide, administered every 3 weeks) vs dose-dense FEC14 (the same regimen repeated every 2 weeks). HER2 status was determined for 731 of 1214 patients. Statistical analyses were performed to test for interaction between treatment and HER2 status with respect to event-free survival (EFS) and overall survival (OS); EFS and OS were compared within each HER2 subgroup and within each treatment arm. Median follow-up was 6.7 years. Among FEC21-treated patients, both EFS (HR = 2.07; 95% CI 1.27-3.38) and OS (HR = 2.47; 95% CI 1.34-4.57) were significantly worse in HER2+ patients than in HER2- patients. Among FEC14-treated patients, differences in either EFS (HR = 1.21; 95% CI 0.65-2.24) or OS (HR = 1.85; 95% CI 0.88-3.89) between HER2+ and HER2- patients were not statistically significant. Interaction analysis suggested that the use of dose-dense FEC14 might remove the negative prognostic effect of HER2 overexpression on EFS and OS. Our data suggest a potential role of HER-2 overexpression in predicting the efficacy of dose-dense epirubicin-containing chemotherapy and the need to confirm this hypothesis in future prospective studies.