Delayed initiation of adjuvant chemotherapy in older women with breast cancer

Background: Adjuvant chemotherapy benefits early-stage breast cancer (BC) patients. Older women receive guideline-adherent treatment less frequently and experience treatment delays more frequently. We evaluated factors associated with delaying adjuvant chemotherapy and the delays’ survival impact in a large population–based cohort of elderly BC patients. Methods: Patients age >66 years diagnosed 2001-2015 with localized or regional BC were identified in the SEER-Medicare and Texas Cancer Registry-Medicare databases. Time from surgery to chemotherapy (TTC) was categorized into four groups: 0-30, 31-60, 61-90, and >90 days. We identified predictors of delays, estimated overall (OS) and BC-specific (BCSS) survival, and determined the association between TTC and outcome adjusting for other variables. Results: Among 28,968 women (median age 71 years), median TTC was 43 days. 10.7% of patients experienced TTC >90 days. Older age, Black or Hispanic race/ethnicity, unmarried status, more comorbidities, hormone receptor-positivity, mastectomy, Oncotype DX testing, and full state buy-in were associated with increased risk of delay. Five-year OS estimates by TTC group were 0.82, 0.81, 0.80, and 0.74, respectively (p<.001). BCSS demonstrated a similar trend (p<.001). Chemotherapy delay was associated with worse OS (HR=1.33, 95%CI 1.25-1.40) and BCSS (HR=1.39, 95%CI 1.27-1.53). In subgroup analysis, delayed chemotherapy was associated with worse OS and BCSS among patients with hormone receptor–positive (HR=1.56, 95%CI 0.97-2.51), HER2-positive (HR=1.99, 95%CI 1.04-3.79), and triple-negative (HR=2.15, 95%CI 1.38-3.36) tumors. Conclusion: Chemotherapy delays are associated with worse survival in older BC patients. Providers should avoid delays and initiate chemotherapy ≤90 days after surgery regardless of patients’ BC subtype or age.