Importance of clear resection margins in anorectal malignant melanoma

Background: Anorectal melanoma is rare and surgery is the recommended primary treatment. There has been some debate whether abdominoperineal resection (APR) or local excision is most appropriate. The aim of this study was to provide a population-based analysis of symptoms, treatment and outcome. Methods: From the Swedish National Cancer Registry, 251 patients with anorectal melanoma were identified from 1960 to 1999. Medical reports were collected and reviewed retrospectively. R0 resection was defined by clear macroscopic margins and a pathology report showing a margin greater than 10 mm. Survival was compared with the log rank test, and Cox multivariable analysis was performed. Results: A-PR and local excision was pet-formed in 66 and 86 patients respectively. Median survival after surgery was 14 months, with no statistically significant difference between the two groups. Seventy-two patients in whom an R0 resection was achieved, irrespective of approach, had a significantly better overall 5-year survival rate than patients with involved margins (19 versus 6 per cent; P < 0.001). Multivariable analysis showed resection status and tumour stage to be independent prognostic variables. Conclusion: Both A-PR and LE seem appropriate for anorectal melanoma provided clear margins can be achieved; prognosis is poor regardless of surgical approach.