Survival Benefit of Chemotherapy According to 21-Gene Recurrence Score in Young Women with Breast Cancer

Background. Initial trials evaluating Oncotype DX, reported as a recurrence score (RS) from 0 to 100, were not powered to evaluate overall survival, and premenopausal women were underrepresented. The purpose of this study was to explore the benefit of chemotherapy according to RS among younger women eligible for oncotype testing.Methods. Women aged 40-50, diagnosed with HR -positive, HER2-negative breast cancer between 2010 and 2017 were selected from the National Cancer Database (NCBD). Patients were grouped by age, RS, nodal status, and chemotherapy receipt. Kaplan-Meier curves were used to compare unadjusted overall survival (OS) between the groups, and log-rank tests were used to test for a difference between groups. Cox proportional hazards models were used to examine the association between select factors and OS.Results. A total of 15,422 patients met inclusion criteria, 45.3% of whom received chemotherapy. Median follow-up time was 66.4 (50.6-86.6) months. Patients who received chemotherapy were more likely to have higher-stage and higher-grade tumors, tumors that were PR-negative, and have higher RS (p < 0.001 for all). RS was prognostic for OS regardless of nodal status. After adjustment, chemotherapy was associated with a significant improvement in OS only in the pN1 RS 31-50 subgroup (p = 0.02).Conclusions. RS retains its prognostic value in younger patients with early stage HR-positive, HER2-negative breast cancer. Chemotherapy survival benefit was limited to patients aged 40-50 with pN1 disease and RS of 31-50. Therefore, chemotherapy decision-making should be especially preference-sensitive in women aged 40-50 with intermediate RS, where it may not provide a survival benefit for many women.