EP640 - A Single Center Retrospective Review of Anal Melanoma

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Purpose/Background: Anal melanoma is a rare, aggressive malignancy with typical delay in diagnosis and poor prognosis. As such, disease presentation, pathogenesis and best treatment practices are poorly understood with no current standardized treatment guidelines. We aimed to characterize patient cases of anorectal melanoma at a single comprehensive cancer center to contribute to our growing scientific understanding of the presentation and treatment of this disease.

Methods/Interventions: All patients at a single comprehensive cancer center with a confirmed diagnosis of anal melanoma and treatment beginning from July 2014 to July 2024 were retrospectively reviewed. Demographics, clinical, and outcomes data were collected for each patient. The primary outcome was survival at 1 year.

Results/Outcomes: There were 25 patients identified with a diagnosis of anal melanoma during the study period. Patients were 68% female (17 patients), with 13 (52%) identifying as white, 11 (44%) as Hispanic, and 1 (4%) as Asian. Average age at diagnosis was 67.2 years (age range: 47-80 years). 13 patients (52%) were found to be stage 3 or higher at the time of diagnosis. The most common symptoms at presentation were bright red blood per rectum (18 patients, 72%) and anal pain (8 patients, 32%). Of note, 2 patients (8%) were asymptomatic and diagnosed with screening colonoscopy. 6 patients (24%) were diagnosed after undergoing hemorrhoidectomies with pathology incidentally revealing anorectal melanoma.12 patients (48%) had undergone colonoscopy without evidence of malignancy within 10 years of diagnosis. 10 patients (40%) had lesions located in the rectum, 12 (48%) in the anorectum, and 3 (12%) were in the anus. 20 patients underwent surgical intervention with 14 undergoing wide local excision/transanal excision and 6 patients undergoing abdominoperineal resection. Of the patients that underwent wide local excision/transanal resection, 2 (14%) received adjuvant chemotherapy (carboplatin/placitaxel) and 4 (28.5%) received adjuvant radiation therapy. Immunotherapy was the most commonly utilized systemic treatment modality with 20 patients (80%) receiving immunotherapy, 8 (32%) neoadjuvantly. A combination of nivolumab and ipilimumab was the most commonly administered immunotherapy regimen (10 patients, 40%). Radiation therapy was used in 9 patients (36%) with no standardized dose for therapy. Four patients (16%) had confirmed recurrence of disease at an average of 37 months (range 12-60 months). Survival rate at 1 year was 76%. 7 patients had documented deaths, 5 of which had metastatic disease at the time of diagnosis.

Conclusion/Discussion: Anorectal melanoma is a rare cancer with symptomatology mimicking that of benign anorectal disease, further complicating the diagnosis. Surgical and medical treatment of this disease varies widely, and mortality remains substantial. Further prospective studies with larger patient populations are needed to inform the development of treatment guidelines for anorectal melanoma to improve patient outcomes.