Primary tumor removal improves the prognosis in patients with stage IV breast cancer: A population-based study (cohort study).

Adjuvant therapy including chemotherapy, hormonal therapy, and radiotherapy were often used as a common stereotypy for female stage IV breast cancer rather than surgery. This study aimed to define the role of local surgery in metastatic breast cancer. Female metastatic breast cancer patients were identified in the Surveillance, Epidemiology, and End Results (SEER) program data (2010-2013). We compared survival time between patients who received primary tumor removal (PTR) versus those who did not. Multivariate Cox regression models and competitive risk models were built to adjust potential confounders. Of 7669 female stage IV breast cancer patients, 2704 (35.3%) had surgery on their breast tumor and 4965 (64.7%) did not. In the entire cohort, women who underwent PTR had a 45% reduced risk of breast cancer-related death (multi-adjusted hazard ratio [HR], 0.55; 95% CI, 0.50 to 0.60) compared with women who did not undergo PTR (P < 0.001). In a cause-specific hazard model (CS model), the multivariable HRs (95% CI) for the association of PTR with breast cancer related-death were 0.54 (0.50-0.60) in the multivariate-adjusted analysis. Similar results were also observed in the sub-distribution hazard function model (SD model) with corresponding multivariate HRs (95%CI) of 0.57 (0.52-0.63). Our study suggested that PTR was associated with improved survival in female stage IV breast cancer patients. The role of PTR in these patients needs to be re-evaluated.