Effect of adjuvant chemotherapy in patients with ER + /HER2- breast cancer, assessed by propensity score matching: significance of nuclear grade and nodal status.

BACKGROUND Survival benefits of chemotherapy (CT) differ among patients with estrogen receptor-positive (ER +) breast cancer. This study investigated the survival benefits of CT for ER + and human epidermal growth factor receptor 2-negative (HER2-) breast cancer (BC) patients by propensity score matching (PSM). METHODS Patients with stages I-IIIER + /HER2- BC were enrolled in this study. The primary endpoints were 5-year recurrence-free survival (RFS) and overall survival (OS) in the non-CT and CT groups of the selected population matched by PS. The PS was analyzed by a logistic regression model with factors those influence provided indication of chemotherapy [tumor size, nuclear grade (NG), progesterone receptor, and nodal status]. RESULTS This study enrolled 895 patients between 2000 and 2015. The median follow-up period was 5.7 years. Overall, the 5-year RFS was 94.3% and 90.1% in the non-CT and CT-treated groups, respectively (p = 0.106). The 5-year OS was 97.5% in the non-CT group and 95.6% in the CT group (p = 0.047). Using PSM, 236 patients were selected. After matching, both the 5-year RFS and the 5-year OS were higher in the CT group than in the non-CT group (96.8% vs. 82.7%, p = 0.003 and 100% vs. 91.9%, p < 0.001, respectively). Particularly in the case of the node negative/NG3 and 1-3 node positive/NG2 patients after PSM, the 5-year RFS was significantly higher in the CT group than in the non-CT group (p = 0.041 and p = 0.006, respectively). CONCLUSION After PSM, CT significantly improved both the RFS and OS of ER + / HER2- BC patients, especially for node negative/NG3 and 1-3 node positive/NG2 patients.