1) Characterize changes in the surgical treatment of anorectal melanoma over time. 2) Determine if the extent of surgical resection is associated with outcome. 3) Identify prognostic factors correlating with survival.

Although early data suggested improved survival in patients undergoing abdominoperineal resection (APR) for primary anorectal melanoma, such an aggressive approach may be unwarranted as distant relapse rates are high. We have seen a trend toward less aggressive surgical treatment of the local disease over the past 20 years.

A retrospective review was performed of all patients with anorectal melanoma treated at our institution between 1984 and 2003. Extent of primary resection and pathologic factors were studied.

Forty-six patients underwent a curative resection with a median follow-up of 29 months, and 5-year disease-specific survival (DSS) rate of 35%. While patient and tumor characteristics remained similar, there was a dramatic shift in surgical treatment toward less radical procedures. Prior to 1997, the majority of patients (15 of 21, 71%) underwent APR. After 1997, the majority of patients (21 of 25, 84%) underwent local excision (LE) (P < 0.0001). Local recurrence was noted in 11 of 46 (24%) patients: 4 of 19 (21%) who underwent APR and 7 of 27 (26%) who underwent LE (P = not significant). Five-year DSS was similar: 34% following APR and 35% following LE. Tumor perineural invasion (PNI) was the only factor identified as an independent predictor of worse outcome (P = 0.01).

The extent of surgical treatment is not associated with outcome in primary anorectal melanoma. Therefore, LE of the primary tumor is recommended when technically feasible. The presence of PNI is an important prognostic factor and should be considered in future clinical trials.