A Real-World Data Retrospective Cohort Study of HER2-positive, Early-Stage Breast Cancer in Patients 70 Years of Age or Older: Natural History, Treatment Patterns, and Outcomes

We conducted a retrospective study of 395 patients 70 years of age or older with resectable HER2-positive breast cancer. Most patients had tumors with high nuclear-grade T2 tumors and received surgical treatment first. Most patients received HER2-targeted systemic treatment in the adjuvant setting only. Older age was associated with increased hazard of recurrence or death. Purpose: Early-stage human epidermal growth factor receptor 2-positive (HER2-positive) breast cancers (BCs) are routinely treated with intense perioperative chemotherapy combined with HER2-targeted agents. There is thus an unmet need for knowledge about treatment patterns and outcomes among patients 70 years of age or older, as this is an under-represented subset of patients in large clinical trials. Methods: We used a deidentified cohort derived from a nationwide electronic health record database to conduct a retrospective cohort study of patients with HER2-positive BCs. Descriptive statistics were used to evaluate tumor characteristics, treatment patterns across age groups, and pathologic complete response rates. We used Kaplan-Meier sur vival cur ves to estimate recurrence-free and overall survivals; Cox proportional methods were used for adjustments with covariates of interest, including age as a categor ical var iable. Results: We included 395 patients with HER2-positive stage I to III BCs who were 70 years of age or older. Most patients had tumors with high nuclear-grade T2 tumors, and received surgical treatment first. Most patients (61.7%) who received HER2 therapies underwent treatment in the adjuvant setting; paclitaxel and trastuzumab combination was the most commonly used adjuvant regimen. Older age was associated with increased hazard of recurrence or death. We did not detect significant evidence of decline in performance status, but there was modest weight drop after perioperative HER2 treatments. Conclusion: Findings suggest that patients in this older-age cohort were treated with de-escalated perioperative strategies and had poorer outcomes; our findings should be validated in future studies.