Impact of surgical management of primary tumors in stage IV breast cancer patients: a retrospective observational study based on SEER database

OBJECTIVES: Although primary tumour surgery could prolong survival for patients with stage IV breast cancer, how to select candidates for primary tumour surgery is still a challenging problem for medical oncologists. DESIGN: This study is a retrospective database study. SETTING AND PARTICIPANTS: In this study, we aimed at evaluating the primary site surgery effect and select the beneficial subgroups. 13 618 patients with stage IV breast cancer, diagnosed between 2010 and 2015, were collected from SEER*Stat database. INTERVENTIONS: Based on the local surgery at primary tumour site, patients were categorised into three groups: primary tumour surgery performed group, recommended for primary tumour surgery but refused (RBR) group and surgery not recommended (NR) group. PRIMARY AND SECONDARY OUTCOME MEASURES: All-cause survival and breast cancer-specific survival (BCSS). RESULTS: Univariate Cox regression analyses showed that, compared with surgery group, patients in non-surgery (RBR and NR) groups tend to be older, T4, N0/NX, triple-negative and visceral metastatic. For both all-cause survival and BCSS, non-surgery, advanced T stage, triple-negative BC (TNBC) and visceral metastases were significant risk factors. Primary tumour surgery showed benefits for both all-cause survival (HR=0.44, 95% CI=0.39–0.49, p<0.0001) and BCSS (HR=0.43, 95% CI=0.38–0.49, p<0.0001). However, after propensity score matching, primary tumour surgery failed to demonstrate significant benefits for TNBC (HR=0.96, 95% CI=0.60–1.53, p=0.851) and patients with visceral metastases (HR=0.90, 95% CI=0.60–1.36, p=0.62). CONCLUSION: Surgery was associated with prolonged survival in stage IV breast cancers, but not in patients with TNBC and visceral metastases.