The prognostic role of surgery and a nomogram to predict the survival of stage IV breast cancer patients

BACKGROUND: Since numerous retrospective studies and prospective trials have shown divergent results, whether the surgical excision of the primary tumor results in survival benefits for de novo stage IV breast cancer patients is inconclusive. Consequently, we need a prediction model of prognosis, judge the efficiency of breast surgery, and identify the advanced breast cancer patients who would benefit from surgery. METHODS: We analyzed the data of 2,747 metastatic breast cancer patients (the surgery group) and 4,508 patients (the non-surgery group) from the Surveillance, Epidemiology, and End Results (SEER) database during 2010–2015. Propensity score matching (PSM) was used to attain a balance between the covariates of both groups. We then assessed the potential risk factors for the breast cancer-specific survival (BCSS) of patients in the non-surgery group by Cox regression and constructed a nomogram to predict BCSS. All the patients were classified into different risk groups based on the median risk score obtained from the nomogram. The hazard ratios of BCSS and overall survival (OS) of patients in the two groups were calculated. RESULTS: After PSM, 2,288 patients severally in the two groups (the surgery group and the non-surgery group) were enrolled in the study. A nomogram incorporating 13 potential risk factors (i.e., age, race, cohabitation status, income, tumor grade, histotype, tumor size, lymph node status, molecular subtype, metastasis to brain, liver, lung, and chemotherapy) was constructed using the data of patients in the non-surgery group. The C statistics for the internal (patients in the non-surgery group) and external (patients in the surgery group) validation of the nomogram were 0.70 [95% confidence interval (CI), 0.69–0.71] and 0.73 (95% CI, 0.72–0.74), respectively. In the low-risk group, patients in the surgery group had lower risks of breast cancer-specific mortality (BCSM) (hazard ratio =0.53; 95% CI, 0.47–0.59; P for interaction =0.014) and overall mortality (OM) (hazard ratio =0.52; 95% CI, 0.46–0.58; P for interaction =0.002) than those in the non-surgery group. CONCLUSIONS: Breast surgery might improve the survival of metastatic breast cancer patients in the low-risk group. The established nomogram could provide a reference for clinicians in enabling personalized treatment among advanced breast cancer patients.