Prolonged overall survival following metastasectomy in stage IV melanoma.

Objective: 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 < 0.001; CI 95% (0.495-0.545)] as well as when analysing solely M1a metastasectomy patients [Hazard Ratio = 0.546, P < 0.001; CI 95% (0.456-0.653)], lung (M1b) metastasectomy patients [Hazard Ratio = 0.389, P < 0.001; CI 95% (0.328-0.462)] and visceral (M1c) metastasectomy patients [Hazard Ratio = 0.474, P < 0.001; CI 95% (0.434-0.517)].

Conclusions: Metastasectomy for Stage IV melanoma is independently associated with improved OS in metastatic cases involving the skin, lung and visceral organs.