Treatment-associated survival outcomes in real-world patients with de novo metastatic triple-negative breast cancer: Age as a significant treatment effect-modifier

Purpose: Evidence for optimizing the first-line chemotherapy for patients with metastatic triple-negative breast cancer (mTNBC) is lacking. This study assessed the utilization patterns of chemotherapy and associated survival outcomes in de novo mTNBC patients. Methods: Taiwan's cancer registry was utilized to extract study patients with newly-diagnosed breast cancer during 2011–2015 and confirmed metastatic triple-negative status. The patients’ medical records (e.g., diseases, treatments) and death status were obtained from the National Health Insurance Research Database. Utilization of first-line chemotherapy regimens was analyzed and associated survival outcomes were assessed using Cox models. Results: 93.60% of the mTNBC patients (n = 297) received chemotherapy, where combination regimens (75.54%) were more common than single-agent regimens (24.46%) in the first-line setting. A non-statistically lower all-cause death associated with combination versus single-agent chemotherapy (hazard ratio: 0.830 [0.589, 1.168]) was observed. Age was identified as a significant effect-modifier in treatment-associated survival outcomes (p = 0.008); younger patients (aged < 40 and 40–59 years) versus older patients (aged ≥ 60 years) had a lower all-cause mortality when receiving combination versus single-agent chemotherapy. A lower all-cause mortality associated with taxane- versus non-taxane-based therapy was revealed among those on single-agent chemotherapy (hazard ratio: 0.557 [0.311, 0.999]). Conclusion: Generally, single-agent and combination chemotherapies yielded comparable survival outcomes as the first-line treatment for de novo mTNBC. Younger patients may benefit more from combination regimens, in terms of better survival outcomes. Single-agent chemotherapy may be preferable as the first-line choice for elderly patients who are vulnerable to the toxicity of multiple chemotherapy agents.