Research on the Effects of Chemotherapy on Survival Outcomes for Older Patients with Primary Triple-Negative Breast Cancer after Surgery: A Propensity Score Matching and Competing Risk Analysis of the SEER Database

Abstract

Background: The population of older women (≥70 years old) with triple-negative breast cancer (TNBC) is increasing, but there are few prognostic studies for these patients. In the study, we explored the effects of chemotherapy on breast cancer-specific death (BCSD) and other cause-specific death (OCSD) in older patients with TNBC. Methods: In accordance with the inclusion and exclusion criteria, we extracted primary TNBC older patients (≥70 years old) from the Surveillance, Epidemiology, and End Results (SEER) database from 2010 to 2019. We used propensity score matching (PSM), cumulative incidence function (CIF) and multivariate Fine and Gray competitive risk analyses to explore the effects of chemotherapy on survival for older patients with primary TNBC after surgery. Results: After one-to-one matched PSM analysis, we identified 2478 primary TNBC patients (≥70 years old) finally. CIF analysis showed that the 3-year, 5-year and 8-year mortalities were 15.34%, 20.30% and 23.73% for BCSD, and 7.36%, 13.20% and 23.02% for OCSD. The survival analysis showed that patients who received chemotherapy had a better overall survival than those who did not received chemotherapy (hazard ratio 0.72, 95% confidence interval 0.63–0.82, p < 0.001). There was no difference in BCSD between older patients with chemotherapy and no chemotherapy. The OCSD rate for patients with chemotherapy was lower than that of those with no chemotherapy (Gray’s test, p < 0.001). Diseases of heart were the most common cause of death in elderly patients with TNBC. After multivariate Fine and Gray competitive risk, age in diagnosis, race black, tumor grade, T status, N status and receiving radiotherapy were proven to be independent predictive factors of BCSD. Meanwhile, age in diagnosis, radiotherapy status, and chemotherapy status were proven to be independent predictive factors of OCSD. Conclusions: For older patients (≥70 years old) with TNBC, chemotherapy improved overall patient survival by reducing the rates of OCSD, but not by reducing the rates of BCSD. The impact of non-cancer causes of death on the prognosis of older cancer patients should not be ignored.