Efficacy of immune checkpoint inhibitors in patients with anorectal melanoma in association with immune-related adverse events: a case series

Anorectal melanoma (AM) is a rare subtype of mucosal melanoma with a poor prognosis. Given its rarity compared to its cutaneous counterpart, the benefits and side effects of immune checkpoint inhibitor (ICI) therapy and the relationship between side effects and prognosis remain unclear. Herein, we describe the clinical presentation of five patients with AM treated with ICI as well as their relationship to the treatment course and the development of immune-related adverse events (irAEs). Three patients received sequential or concurrent administrations of nivolumab and ipilimumab, one received nivolumab alone, and one received ipilimumab alone. The response rate (RR) and disease control rate (DCR) were 40% and 80%, respectively. Pituitary and hepatic dysfunctions were the most common irAEs observed (40% each), followed by thyroid, diarrhea, and renal dysfunctions (20% each). The RR was 67% in patients with irAEs while no response was observed in patients without irAEs. DCR was 100% and 50% in patients with and without irAEs, respectively. Overall survival was 34 months in irAE and 8.75 months in non-irAE cases, with a longer survival trend in irAE cases. ICI therapy was effective and well-tolerated by AM patients, with potentially better outcomes for those who experienced irAEs compared to those who did not.