Excision margins and prognosis in cutaneous melanoma: retrospective population-based cohort study.

Background: The impact of surgical excision margin size on the survival of patients with cutaneous melanoma (CM) is controversial. The aim of this study was to assess the impact of excision margins on patient outcomes.

Methods: This retrospective population-based follow-up study analysed data from patients presenting with CM without extranodal disease. The linear distance of CM from the excision margin was assessed microscopically. Regarding overall and melanoma-specific survival estimates, Kaplan-Meier analysis, the Cox proportional hazards model, and the subdistribution hazard ratio of the Fine-Gray model were applied.

Results: Of 3262 patients, a total of 2698 (82.7%) with pathological (p) T1-2 and 564 (17.3%) with pT3-4 CM underwent wide local excision. Multivariable analyses, adjusting for melanoma incidence cohort, age, sex, anatomical site, ulceration, histotype, mitotic count, and tumour-infiltrating lymphocytes, demonstrated that, in pT1-2 CM, surgical excision > 1.1 cm resulted in significant CM-specific survival benefit. In pT4 disease, a CM distance to the surgical margins of < 1.6 cm significantly lowered CM-specific survival.

Conclusion: This population-based study conducted in real-world clinical practice found that the prognosis of patients with pT1-2 CM may benefit from excision margins > 1.1 cm. In pT3-4 CM, margins < 1.6 cm were significantly associated with lower CM-specific survival rates. These findings highlight the need for further prospective studies to evaluate the safety of surgical excision margins in managing primary CM.