Multidisciplinary Management of Anorectal Melanoma: a Retrospective Analysis of Surgical and Systemic Therapies from the National Cancer Database.

Objective: Anorectal melanoma (ARM) represents a problematic scenario due to a 5-year overall survival (OS) rate below 20% and its increasing incidence. Due to its comparable OS, local surgery (LS) has replaced radical surgery (RS). Adjuvant chemotherapy (Adj-CHT) and adjuvant immunotherapy (Adj-IT) are common treatments for ARM, while neoadjuvant immunotherapy (Neo-IT) has not been investigated yet. This study aimed to determine the best treatment to improve the OS.

Methods: Patients with non-metastatic ARM in the National Cancer 1Database (2011-2021) who underwent surgery and received Neo-IT, Adj-IT, or Adj-CHT were included. Two cohorts were created based on the surgical approach (LS or RS). In their respective cohorts, patients receiving Neo-IT, Adj-IT, or Adj-CHT were matched 1:1:1 based on age, tumor size and location, lymphovascular invasion, and nodal disease. Kaplan-Meier analyses compared the different groups' influence on the 3-year OS.

Results: Sixty patients were included in the LS cohort. Among them, there was no difference in the 3-year OS at the Kaplan-Meier analysis (Neo-IT 61%, Adj-IT 47.1%, and Adj-CHT 44%). Thirty-six patients were included in the RS cohort. Kaplan-Meier analysis for this group revealed that Neo-IT was a protective factor for 3-year OS (Neo-IT 71%, Adj-IT 11%, Adj-CHT 8%; p-value = 0.002).

Conclusions: Neo-IT + RS seems to improve the 3-year OS compared to the other common treatments for ARM. Neo-IT + RS can be considered a valuable treatment since prospective trials are challenging for rare diseases. When RS is not feasible, Neo-IT + LS may be beneficial as the 3-year OS reaches 61%.