Sex differences in survival of anal melanoma: An analysis of the United States National Cancer Database.

e21607 Background: Mucosal melanoma is a rare, more aggressive subtype of melanoma, accounting for < 2% of all melanomas and associated with a poorer prognosis than cutaneous malignant melanomas. It can occur in any part of the body that contains melanocytes, including anywhere along the gastrointestinal tract with the anorectal region being the most common location. Patients with anorectal melanoma typically present with late-stage disease and treatment options are not well established given the rarity of the disease. Although sex differences in survival have been observed for cutaneous melanomas, with females having a survival advantage over males, sex differences in survival have not been well established in anal melanoma. This study aimed to compare the survival outcomes of anal melanoma between male and female patients using a national registry from the United States. Methods: Adult patients who were diagnosed with anal melanoma were identified from the National Cancer Database (NCDB) of Anal Cancer from 2005 to 2022 based on ICDO-3 codes. Patients undergoing palliative care were excluded. Overall survival (OS) was analyzed using Kaplan-Meier (KM) plots, log-rank tests, and Cox proportional hazard models that controlled for age, race and ethnicity, primary payor, income, education, facility type/location, comorbidities, treatment, and TNM staging. Results: Among the patients with anal melanoma, 594 were males and 873 were females. Males had a shorter mean OS (p < 0.01; Table). KM curves of the two groups were created, and a log-rank test showed a statistically significant difference in survival rates (p = 0.04). After multivariable analysis, OS remained significantly lower in male patients (HR 1.240, 95 CI 1.087-1.416, p < 0.01). Landmark survival rates of males were lower than that of females at 3 years [0.338 (95 CI 0.299-0.380) vs 0.400 (95 CI 0.366-0.435), p = 0.02] and 5 years [0.230 (95 CI 0.194-0.269) vs 0.284 (95 CI 0.250-0.319), p = 0.02] (Table). Conclusions: Males with anal melanoma exhibit worse survival outcomes compared to females, which is consistent with the known survival differences in cutaneous melanoma. Further research is needed to investigate the underlying mechanisms behind these differences and to develop targeted treatment strategies. Overall mortality, mean survival time, and landmark survival rates between male and female patients with anal melanoma. Male(n = 594) Female(n = 873) p-value Overall mortality (n, %) 421 (70.88%) 581 (66.55%) 0.09 Survival month (mean ± SE) 48.35 ± 2.73 59.41 ± 2.71 <0.01 Landmark survival rates (%, 95 CI) 6-month 0.883 (0.853-0.907) 0.885 (0.861-0.905) 0.91 1-year 0.734 (0.695-0.769) 0.744 (0.711-0.771) 0.67 2-year 0.501 (0.458-0.543) 0.511 (0.475-0.545) 0.71 3-year 0.338 (0.299-0.38) 0.400 (0.366-0.435) 0.02 5-year 0.230 (0.194-0.269) 0.284 (0.366-0.435) 0.02 Abbreviations: CI, confidence interval; SE, standard error.