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

Purpose: 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. Methods and Materials: This retrospective cohort study included all patients with pelvis-confined anorectal melanoma undergoing sphincter-sparing local excision and adjuvant radiation therapy (RT) at our institution between 1989 and 2020. Patterns of care and predictors of outcome were evaluated. Results: 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 and the 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, whereas no node-positive patient treated subsequently received this treatment. Patients treated before 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. Conclusions: 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.