Outcomes After Sphincter-Sparing Local Therapy for Anorectal Melanoma: 1989 to 2020

The treatment paradigm for patients with anorectal melanoma eligible for sphincter-sparing excision has evolved over time. This study examines outcomes across a 30-year era in this rare disease with poor prognosis.This retrospective cohort study included all patients with pelvis-confined anorectal melanoma undergoing sphincter-sparing local excision and adjuvant RT at our institution between 1989-2020. Patterns and predictors of outcome were evaluated.Of the 108 patients included, 92 (85%) presented with clinically uninvolved nodes. For clinically node-negative patients the sentinel lymph node biopsy rate increased from 18/43 (42%) before 2008 to 38/49 (78%) subsequently, while use of inguinal nodal RT decreased from 33/35 (94%) before 2003 to 1/57 (2%) subsequently. All clinically node-positive patients treated before 2003 received inguinal nodal RT while no node-positive patient treated subsequently received this treatment. Patients treated prior to 2016 mostly received biochemotherapy and those treated since 2017 mostly received immune checkpoint inhibitors. With median follow-up of 32 months, 77 patients (71%) recurred. Three-year actuarial outcomes were: 84% local control, 64% nodal control, 38% distant metastasis-free survival, 30% disease-free survival, and 51% melanoma-specific survival. Ostomy-free survival at last follow-up was 95%. Factors contributing to outcome were identified. Outcomes for patients treated in the contemporary era (2017+) were not significantly better than those treated earlier.Sphincter-sparing surgery followed by adjuvant RT results in excellent local control and ostomy-free survival for locally resectable anorectal melanoma. Overall oncologic outcomes continue to be poor, reinforcing the need to identify more effective therapies.