Surgical resection margin for T3-T4 primary acral melanoma: a multicenter retrospective cohort study.

Although the National Comprehensive Cancer Network (NCCN) guidelines include clear recommendations for the appropriate resection margins in non-acral cutaneous melanoma, the required margin for acral melanoma is controversial. In this retrospective study, we aimed to investigate whether narrow-margin excision is warranted for thick acral melanoma. Records from 277 melanoma patients with stage T3-T4 disease who underwent radical surgery in three centers in China from September 2010 to October 2018 were reviewed. Clinicopathologic data, including age, gender, excision margin (1-2 cm versus ≥ 2 cm), Clark level, Breslow thickness, ulceration, N stage and adjuvant therapy, were included for survival analysis. The patients were followed up until death or March 31, 2021. Log-rank and Cox regression analyses were used to identify prognostic factors for overall survival (OS), disease-free survival (DFS) and local and in-transit recurrence-free survival (LITRFS). Among all enrolled patients, 207 (74.7%) had acral melanoma, and 70 (25.3%) had non-acral cutaneous melanoma. No significant difference in baseline characteristics was identified between non-acral and acral melanoma, except for age (p = 0.004), gender (p = 0.009) and ulceration (p = 0.048). In non-acral melanoma, a resection margin of 1-2 cm was a poor independent prognostic factor for OS [p = 0.015; hazard ratio (HR) (95% CI), 0.26 (0.009-0.77)] and LITRFS [p = 0.013; HR (95% CI), 0.19 (0.05-0.71)] but not for DFS [p = 0.143; HR (95% CI), 0.51 (0.21-1.25)]. Forty-three (20.8%) patients in the acral melanoma group had a 1-2-cm resection margin. The resection margin was not correlated with patients' OS (p = 0.196 by log-rank analysis, p = 0.865 by multivariate survival analysis), DFS (p = 0.080 by log-rank analysis, p = 0.758 by multivariate survival analysis) or LITRFS (p = 0.354 by log-rank analysis) in acral melanoma. As recommended in the NCCN guidelines, a resection margin ≥ 2 cm is required for non-acral cutaneous melanoma. Meanwhile, a narrow resection margin (1-2 cm) may be safe for patients with acral melanoma.