Utility of adjuvant chemotherapy in early-stage, estrogen receptor-positive breast cancer patients under 50 years with a 21-gene recurrence-score of 16-25: A retrospective analysis using the National Cancer Database.

Abstract

e12501 Background: The TAILORx trial showed that addition of adjuvant chemotherapy (AC) to endocrine therapy (ET) had no advantage in estrogen receptor (ER)+, HER2-, node negative (N0) breast cancer (BC) patients with an intermediate (11-25) 21-gene recurrence-score (RS). However, a subgroup analysis revealed that in women ≤ 50 years, AC had a lower rate of distant recurrence if the RS was 16-25. Using a large national database, we studied the utilization of AC in the aforementioned subset. Methods: The 2004-2018 National Cancer Database BC cohort was used to include female patients of 18-50 years. Inclusion criteria were N0, M0 patients with any T stage, RS 16-25, ER+/PR± and HER2-. Patients who received neoadjuvant chemotherapy were excluded. Logistic regression was used to evaluate AC utility trends. Kaplan-Meier (KM) and multivariate (MV) propensity score (PS) weighted Cox model were used to compare survival between patients without and with AC use. Results: Of the 15,792 patients, 4808 (30.45%) received AC. Median RS was 18 and 21 in patients without and with AC. Factors associated with AC use were higher T stage, poor and moderately differentiated tumors, age <40, care at an academic center, Caucasian race, patients undergoing mastectomy, regional lymph node (RLN) surgery, ET and Radiation Therapy (RT). KM survival at 10 years was better with AC [96.2% vs 91.6%]. Patients without AC had worse survival [Hazard Ratio (HR)=1.683, 95% Confidence Interval (CI): 1.392-2.036, p<0.0001] (Table). Conclusions: In this analysis,AC use had a 5% improvement in 10 year overall survival, in contrast to TAILORx trial which only showed a disease free survival benefit. Whether the benefit was due to direct cytotoxicity or ovarian function suppression effect of AC remains to be seen. In clinical practice, AC use is determined based on patient and tumor characteristics. Limitations of our study include non-population-based data and the possibility of cofounding despite the use of PS matching. [Table: see text]