Prolonged overall survival following metastasectomy in stage IV melanoma

Background/Objectives Current literature supports mixed conclusions regarding the outcomes of metastasectomy in Stage IV melanoma. The objective of this national study was to determine the associations of non-primary site surgery with overall survival (OS) in Stage IV melanoma. Methods The National Cancer Database (NCDB) was queried for all Stage IV melanoma cases diagnosed from 2004 to 2015. Cases missing treatment/staging data or undergoing palliative treatment were excluded (remaining n = 14 034). Patients were separated into 'metastasectomy' (n = 4214, 30.0%) and 'non-metastasectomy' (n = 9820, 70.0%) cohorts. Survival outcomes were analysed using Kaplan-Meier and Cox proportional hazards regressions. Results On univariate analysis, patients with Stage IV melanoma undergoing metastasectomy (median survival: 15.67 month) had greater overall survival compared with those not receiving non-primary surgery (median survival: 7.13 month; 5-year OS 13.2% vs. 5.6%, P < 0.001). M1a patients that underwent non-primary metastasectomy (median survival: 46.36 month) showed greater survival than those that did not (median survival: 15.31 month; P < 0.001). Metastasectomy was undertaken more frequently for cutaneous (M1a) metastasis compared with non-M1a metastasis (34.6% vs. 28.4%, P < 0.001). Of those receiving metastasectomy, 20.3% also received primary site resection, 33.6% radiation, 26.5% chemotherapy and 31.5% immunotherapy. Controlling for covariates on Cox proportional hazard analysis, all metastasectomy patients demonstrated longer survival [Hazard Ratio = 0.519, P CI 95% (0.495-0.545)] as well as when analysing solely M1a metastasectomy patients [Hazard Ratio = 0.546, P CI 95% (0.456-0.653)], lung (M1b) metastasectomy patients [Hazard Ratio = 0.389, P CI 95% (0.328-0.462)] and visceral (M1c) metastasectomy patients [Hazard Ratio = 0.474, P CI 95% (0.434-0.517)]. Conclusion Metastasectomy for Stage IV melanoma is independently associated with improved OS in metastatic cases involving the skin, lung and visceral organs.