Impact of Lateral Margin Adequacy on Survival in Cutaneous Melanoma: An Asian Retrospective Cohort Study

ABSTRACT The optimal surgical margin for cutaneous melanoma remains controversial, particularly in anatomically constrained areas such as the acral regions. We conducted a retrospective cohort study of 79 patients with invasive cutaneous melanoma treated at National Cheng Kung University Hospital between 2012 and 2024, including 51 cases of acral lentiginous melanoma (ALM). Patients were categorized as having adequate surgical margins (per NCCN guidelines) or inadequate but histologically tumor‐free margins. Survival outcomes, including overall survival (OS), progression‐free survival (PFS), local recurrence‐free survival (LRFS), and melanoma‐specific survival (MSS), were analyzed using Kaplan–Meier estimates and Cox proportional hazards models after a median follow‐up of 60 months. No significant differences were observed in OS, LRFS, or MSS between the two groups. Although univariate analysis suggested a difference in PFS, the association did not persist in multivariate analysis, where margin inadequacy was not independently associated with poorer outcomes (OS: HR 1.81, 95% CI 0.84–3.90, p = 0.13; PFS: HR 1.87, 95% CI 0.90–3.87, p = 0.093). Subgroup analyses of ALM and high‐risk tumors (Breslow thickness > 2 mm) yielded consistent results, showing no significant differences in oncologic outcomes. In conclusion, our study showed that inadequate but histologically tumor‐free excision margins may not independently compromise survival outcomes in cutaneous melanoma. A narrower margin may be acceptable in selected patients when wider excision is precluded by anatomic or functional constraints.