Background: Primary gastrointestinal (GI) melanomas, compared with cutaneous melanomas, have a much lower incidence. As a result, there is a paucity of data regarding their presentation, treatment, and prognosis. The aim of this study was to analyze the incidence, patient characteristics, treatment patterns, and survival of primary GI melanomas in comparison with cutaneous melanomas using a population-based cohort.
Methods: Patients diagnosed with primary GI and cutaneous melanomas were identified from Surveillance, Epidemiology, and End Results 1973-2016 data.
Results: A total of 872 primary GI melanomas and 319,327 cutaneous melanomas were identified. GI melanoma incidence increased by an annual percent change of 1.82 (P < 0.05) during the study period. The most common sites for GI melanoma were the anus (50%) and rectum (34%). Compared to cutaneous melanoma, patients diagnosed with GI melanomas were older, women (58% versus 45%), non-White (16% versus 6%), and presented with a higher stage (36% versus 4% distant stage, all P < 0.001). GI melanomas had significantly worse cancer-specific survival (CSS) than cutaneous melanoma. Despite the poor prognosis, the CSS has increased in recent years. Among patients with anorectal melanomas, local excision with chemotherapy and/or radiation had a similar CSS compared with those with major surgery only.
Conclusions: Despite a steady increasing incidence since 1975, GI melanomas are rare, present with advanced stages, and have worse outcomes than cutaneous melanomas. The improved prognosis of these tumors in recent years might reflect the impact of novel targeted treatments and the more common use of local tumor excision over major resections.
Keywords: Anorectal melanoma; Cutaneous melanoma; Gastrointestinal melanoma/cancer; SEER program.
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