Survival benefit of radiotherapy after surgery in de novo stage IV breast cancer: a population-based propensity-score matched analysis

The survival benefit from radiotherapy in stage IV breast cancer has not been fully evaluated. We investigated the survival benefit of radiotherapy after surgery in de novo stage IV breast cancer. Using a population-based database (the Surveillance, Epidemiology, and End Results database 18, 2010-2013), patients diagnosed with de novo stage IV breast cancer were divided into those undergoing surgery alone (no-radiotherapy group) and those undergoing surgery followed by radiotherapy (radiotherapy group). After propensity-score matching (PSM), the cancer-specific survival (CSS) rates were estimated. Multivariate analysis was performed to evaluate the prognostic value of radiotherapy on survival. After PSM, the 3-year CSS rates in the no-radiotherapy (n = 882) and radiotherapy (n = 882) groups were 57.1% and 70.9% (P < 0.001), respectively. On multivariate analysis, radiotherapy after surgery was a significant prognosticator (hazard ratio [HR] 0.572; 95% confidence interval [CI] 0.472-0.693, P < 0.001). Regardless of surgery type and lymph node involvement, the radiotherapy group showed significantly higher CSS rates. For patients who survived six months or more, radiotherapy after surgery demonstrated favorable prognosis compared to surgery alone (HR 0.593; 95%Cl 0.479-0.733, P < 0.001). In conclusion, radiotherapy after surgery increased CSS rates in de novo stage IV breast cancer compared to surgery alone.