A Population-Based Study of the Incidence and Survival of Anorectal Gastrointestinal Stromal Tumor.

BACKGROUND Gastrointestinal stromal tumor (GIST) is the most common type of primary gastrointestinal mesenchymal tumor, but GISTs arising in the anus and rectum are rare. This study aimed to undertake a population-based analysis of the incidence, patient demographics, and survival of patients with anorectal GIST compared with patients with GIST arising from other sites based on the Surveillance, Epidemiology, and End Results (SEER) Program database. MATERIAL AND METHODS The SEER database was used to identify all patients diagnosed with GIST and patients diagnosed with anorectal GIST from 2000 to 2015. The incidence of GIST, baseline clinical and demographic data, tumor stage, and patient survival data were analyzed, including overall survival (OS) and cancer-specific survival (CSS). RESULTS A total of 277 patients with anorectal GIST were identified, with an incidence of 0.018 per 100,000. The incidence of GIST arising from other sites was 0.719 per 100,000. The median age at diagnosis for anorectal GIST was 57.5 years (range, 26-92 years), median tumor size was 6.55 cm (range, 0.6-20 cm), and surgery, but not chemotherapy, improved OS and CSS. Patients with anorectal GIST had a mean 1-year, 3-year, 5-year, and 10year OS of 91.1%, 82.5%, 75.2%, and 58.5%, respectively. Patients with GIST arising at other sites had a mean 1-year, 3-year, 5-year, and 10-year OS of 88.3%, 76.4%, 66.5%, and 46.8%, respectively. CONCLUSIONS Anorectal GIST is a rare tumor that has a better outcome compared with GISTs arising at other sites in the gastrointestinal tract.