Surgical excision margins in primary cutaneous melanoma: A meta-analysis and Bayesian probability evaluation

Surgery is the only curative treatment for primary cutaneous melanoma, therefore it is important to determine excision margins that minimise risk of local recurrence, distant recurrence and death.

MEDLINE, EMBASE and Cochrane CENTRAL were searched from 2009 to 2015. Inclusion criteria were: population/setting - patients with primary melanoma; comparison - narrow versus wide margins; outcomes - overall survival, melanoma-specific survival, recurrence-free survival, and loco-regional recurrence; design - randomized controlled trials (RCTs). Results were pooled using meta-analysis and data explored using likelihood Bayesian probability plots.

Six RCTs with 4233 patients were included. Narrow margins were defined as 1 or 2 cm of clinically normal skin around the melanoma; wide margins as 3, 4 or 5 cm. Hazard ratios (HR) were as follows (HR>1 indicates wide margin better): overall survival 1.09 (95% CI 0.98-1.22; p=0.1); melanoma-specific survival 1.17 (CI 1.03-1.34; p=0.02); recurrence-free survival 1.08 (CI 0.97-1.20; p=0.2); loco-regional recurrence 1.10 (CI 0.96-1.26; p=0.2), with no evidence of heterogeneity between trials for any end point or within subgroup analyses. There was an 94% probability that overall survival was worse with a narrow margin and a 43% probability that it was more than 10% worse in proportional terms (i.e. HR>1.1). Probabilities that narrow margins were worse were 99%, 92% and 92% for melanoma-specific survival, recurrence-free survival and loco-regional recurrence respectively.

Contrary to recommendations in several national guidelines that narrow margins are safe, this systematic review and meta-analysis provides evidence that a narrow margin may lead to a worse outcome than a wide margin.