The Effect of Primary Surgery in Patients with De Novo Stage IV Breast Cancer with Bone Metastasis Only (Protocol BOMET MF 14-01): A Multi-Center, Prospective Registry Study

Background: More evidence shows that primary surgery for de novo metastatic breast cancer (BC) prolongs overall survival (OS) in selected cases. The aim of this study was to evaluate the role of locoregional treatment (LRT) in BC patients with de novo stage IV bone only metastasis (BOM). Methods: The prospective, multicenter registry study BOMET MF14-01 was initiated in May 2014. Patients with de novo stage IV BOM BC were divided into two groups: those receiving systemic treatment (ST group) and those receiving LRT (LRT group). Patients who received LRT were further divided into two groups: ST after LRT (LRT + ST group) and ST before LRT (ST + LRT group). Results: We included 505 patients in this study; 240 (47.5%) patients in the ST group and 265 (52.5%) in the LRT group. One hundred and thirteen patients (26.3%) died in the 34-month median follow-up, 85 (35.4%) in the ST group and 28 (10.5%) in LRT group. Local progression was observed in 39 (16.2%) of the patients in the ST group and 18 (6.7%) in the LRT group (p = 0.001). Hazard of death was 60% lower in the LRT group compared with the ST group (HR 0.40, 95% CI 0.30–0.54, p < 0.0001). Conclusion: In this prospectively maintained registry study, we found that LRT prolonged survival and decreased locoregional recurrence in the median 3-year follow-up. Timing of primary breast surgery either at diagnosis or after ST provided a survival benefit similar to ST alone in de novo stage IV BOM BC patients.