In the United States, adriamycin/cyclophosphamide/paclitaxel/trastuzumab (ACTH) and docetaxel/carboplatin/trastuzumab (TCH) have been widely adopted as systemic adjuvant therapy of human epidermal growth factor receptor 2-positive (HER2+) breast cancer and remain the standard of care for many women with early-stage HER2+ disease. However, no head-to-head comparison of these regimens has been conducted in a clinical trial, and current clinical trial data have limited generalizability because of the exclusion of older women and the low representation of minorities and those with significant comorbidities. Researchers at the University of North Carolina, Chapel Hill, presented their new head-to-head results on Friday, December 9, during the San Antonio Breast Cancer Symposium.
Using Surveillance, Epidemiology, and End Results Program–Medicare data from 2005–2013, the group compared ACTH and TCH in 1,077 patients with HER2+ older than 65 years who were receiving trastuzumab-based adjuvant chemotherapy. Outcomes included toxicity-related hospitalization, survival, and regimen completion (receiving ≥ 270 days of trastuzumab).
A significant shift in treatment regimens occurred during the time of the study: in 2005, 88% of patients received ACTH, but by 2011 that had fallen to only 15%. The group opted to use propensity score matching to account for selection bias (that subsample included 416 women). In the propensity score-matched patients, no differences were seen between the two regimens in healthcare use for chemotherapy-related adverse events or all cause hospitalization.
Overall, patients who received TCH were significantly more likely to complete trastuzumab (89% for TCH versus 77% for ACTH). No differences were noted in any group in the five-year breast cancer-specific survival or overall survival.
Although the ability to evaluate cardiotoxicity in the claims-based data was limited, the researchers said that in the context of limited evidence in older patients, “there appears to be little difference between the two regimens in terms of either toxicity or efficacy.”