Local surgery improves survival in elderly patients with stage IV breast cancer: a population-based retrospective cohort study

Background: Little is known about the role of local therapy in elderly patients with stage IV breast cancer. This study aimed to evaluate the effect of local therapy including surgery and radiotherapy in this kind of population by using the Surveillance, Epidemiology, and End Results (SEER) database.Methods: Eligible patients diagnosed between 2010 and 2015 were selected from the SEER database. Baseline characteristics, way of local therapy and survival information were collected for survival and analysis of prognostic factors. Cause-specific survival (CSS) curves were calculated using the Kaplan-Meier (KM) method and compared by the log-rank test. Cox regression and multivariate competing risk analyses were used to analyze prognosis factors.Results: A total of 1,900 patients were enrolled with the median age of 71 (range, 65 to 95) years. The 5-year CSS of patients with surgery was significantly better than that of those who did not (36.5% vs. 22.4%, P<0.001). Moreover, surgery was an independent protective factor for CSS in both multivariate Cox regression analysis [hazard ratio (HR), 0.588; 95% confidence interval (CI), 0.485-0.643; P<0.001] and multivariate competing risk analysis [subdistribution HR (SHR), 0.620; 95% CI, 0.535-0.718; P<0.001]. Stratified analysis showed that most subgroup patients could benefit from surgery. The 5-year CSS of patients with radiotherapy was comparable to those without radiotherapy (28.9% vs. 26.5%, P=0.060), and radiotherapy was not an independent prognostic factor for CSS (SHR, 1.005; 95% CI, 0.846-1.202; P=0.954). However, subgroup analysis found that patients with moderate grade in histopathology, luminal A, or triple-negative breast cancer (TNBC) subtype could benefit from radiotherapy (all P<0.05).Conclusions: Elderly patients with stage IV breast cancer can benefit from surgical treatment. This study helps to select the appropriate group for local surgery or radiotherapy according to the personal situation of the elderly to obtain the maximum benefit.