Comparison of prognostic factors and survival outcome between gastrointestinal tract and cutaneous invasive malignant melanoma.

Abstract

618 Background: Gastrointestinal melanoma (GIM) is a rare disease. The objective of this study is to compare the overall survival (OS), cancer specific survival (CSS) and prognostic factors of GIM to those of skin melanoma (SKM) using the Surveillance, Epidemiology, and End Results (SEER) registry. Methods: Patients diagnosed with invasive GIM (406) and SKM (173,622) between 1973 and 2008 were identified from the SEER database. Factors analyzed included age (18-40/41-60/61-100), gender, race (White/nonwhite), marital status, stage (localized/regional/distant), year of diagnosis (1973-87/1988-97/1998-2008), and type of treatment (radiotherapy (RT)/surgery). OS and CSS were evaluated using the Kaplan-Meier method. Cox proportional hazards regression analysis examined what factors were prognostic of survival. Results: The median age was 69 and 57 for patients with GIM and SKM, respectively. The GIM group was older with more advanced-stage cancer than the SKM group. Surgery was performed on 85% and 95%, while RT was received by 18% and 2% of GIM and SKM patients, respectively. The GIM group had a median OS and CSS of 15 and 16 months, respectively, while the SKM group had a median OS of 283 months and did not reach a median CSS. Cox analysis showed that SKM had significantly lower risk of total and cancer-specific mortality compared to GIM (Hazard Ratio (HR) 0.40, p<0.0001) and (HR 0.34, p<0.0001). Factors associated with improved OS and CSS in SKM included: age ≤60, female gender, non-white race, early stage, being married, more recent diagnosis, undergoing surgery and not receiving RT. Factors associated with improved OS and CSS in GIM included: age ≤60, early stage, non-white race and undergoing surgery. Subgroup analysis on patients who underwent surgery showed that lymph node status was the only prognostic factor for GIM, while all of the previously identified prognostic factors except for race were associated with OS and CSS for SKM. Conclusions: Outcomes of patients with GIM are inferior to those with SKM. The melanomas in these two sites also have different prognostic factors. Future studies should explore the reasons behind these differences to improve treatment outcomes.