Additional radiotherapy to breast‐conserving surgery is an optional treatment for de novo stage IV breast cancer: A population‐based analysis

BACKGROUND: We aim to assess the value of locoregional treatment (LRT) including breast‐conserving surgery (BCS), mastectomy (MAST), and radiotherapy (RT) in patients with de novo stage IV breast cancer. METHODS: Patients with de novo stage IV breast cancer were retrospectively identified from the Surveillance, Epidemiology, and End Results database between 2004 and 2014. Kaplan‐Meier analysis, log‐rank tests, propensity score matching (PSM), and the multivariate Cox proportional model were used for statistical analysis. RESULTS: A total of 5798 patients were identified including 849 (14.6%), 763 (13.2%), 2338 (40.3%), and 1848 (31.9%) who received BCS alone, BCS+RT, MAST alone, and MAST+RT, respectively. The proportions of receiving BCS decreased from 35.9% in 2004 to 26.2% in 2014 (p = 0.002), and the probability of patients receiving MAST increased from 64.1% in 2004 to 74.8% in 2014 (p = 0.002). Before PSM, there was a significant difference in breast cancer‐specific survival (BCSS) among the treatment arms. Patients who received RT had better BCSS, the 5‐year BCSS was 40.5%, 52.3%, 41.5%, and 47.7% in patients treated with BCS alone, BCS+RT, MAST alone, and MAST+RT, respectively (p < 0.001). In the PSM cohort, patients treated with BCS alone had lower 5‐year BCSS compared to those treated with BCS+RT (43.9% and 52.1%, p = 0.002). However, there were comparable 5‐year BCSS between BCS+RT and MAST alone groups (51.3% and 50.1%, p = 0.872), and BCS+RT and MAST+RT cohorts (51.5% and 55.7%, p = 0.333). Similar results were confirmed in multivariate analysis. CONCLUSIONS: Postoperative RT improves BCSS in patients with de novo stage IV breast cancer, and BCS+RT shows a non‐inferior outcome compared to MAST+RT. BCS+RT may be the optimal local management of de novo stage IV breast cancer.