The development of anti-human epidermal growth factor receptor 2 (HER2) therapies has significantly improved disease outcomes in patients with HER2-positive advanced breast cancer (ABC). However, elderly patients are largely under-represented in clinical trials. We examined treatment patterns and outcomes in an elderly (defined as ≥70) ‘real world’ Australian population.
Data was extracted from the Treatment of Advanced Breast Cancer in the HER2-positive Australian Patient (TABITHA) multi-site clinical registry, and patients stratified according to age (<70 and ≥70 years). Descriptive statistics were used to report baseline characteristics and compared using T-tests and Chi square analyses. Treatment duration and overall survival were calculated via the Kaplan-Meier method.
We identified 319 patients, including 67 patients (21%) aged ≥70. Older patients were more likely to have an Eastern Cooperative Oncology Group performance status of ≥2 (16% vs 3%; p<0.001) and a Charlson Comorbidity Index of ≥2 (13% vs 7%; p<0.001). There were no significant differences in hormone receptor status, de novo metastatic presentation, or presence of visceral disease. A similar proportion of patients in each group received first line HER2-directed therapy, and the duration of therapy was not significantly different. Despite no difference in the proportion of patients who received first-line chemotherapy, older patients demonstrated shorter chemotherapy durations (2.7 months vs 3.5 months; p<0.02). Median overall survival was significantly longer in younger patients (82.4 months vs 42.3 months; hazard ratio, 0.50; 95%CI, 0.29-0.87; p<0.001). In the first-line setting, adverse events rates were higher in the older group (34% vs 20%; p=0.04), including cardiotoxicity (7% vs 0.9%; p=0.02), and on-treatment deaths (5% vs 0%; p=0.01).
Elderly patients with HER2-positive ABC demonstrated shorter chemotherapy durations, poorer overall survival, and increased rates of adverse events despite having similar disease characteristics and treatment patterns. Prospective studies are required to improve outcomes in this population.