A176 SMALL GASTROINTESTINAL STROMAL TUMORS (GISTS): A RETROSPECTIVE ANALYSIS OF EUS SURVEILLANCE

Gastrointestinal stromal tumors (GISTs) are the most common mesenchymal tumors of the GI tract. They are often noted incidentally at endoscopy or cross sectional imaging. Following the identification of such lesions, further investigation via endoscopic ultrasound, often with fine needle aspiration (EUS-FNA) is used to confirm diagnosis. The natural history and appropriate management of small (< 2 cm) GISTs is not well understood and in 2010 the National Comprehensive Cancer Network (NCCN) guidelines recommended surveillance EUS every 6–12 months. To determine if our management strategy for small GISTs was consistent with present guidelines. Secondary outcomes were to identify any barriers to surveillance and determine the natural history of GISTs. A retrospective chart review of all EUS procedures at St. Paul’s Hospital, Vancouver, Canada from 01/05-06/17 was completed. Individuals with small (< 2 cm) GISTs were identified. GIST was defined as a hypoechoic lesion arising from the 2nd or 4th layer of the gastrointestinal wall +/- cytological or histologic diagnosis. Data collected included patient demographics, clinical presentation, initial and subsequent EUS findings, interval between EUS, reasons for not undergoing surveillance EUS, and any pathology. Candidates were then collated based on the presence of GISTs and whether appropriate follow-up occurred based on the National Comprehensive Cancer Network (NCCN) guidelines. This study was approved by the IRB at St. Paul’s Hospital. GISTs were identified by EUS in 143 patients, 69 (48%) had lesions <2 cm in size. Mean age of diagnosis was 64 years (SD: 12.5), with 52% being female. 80% were referred due to incidental findings at initial endoscopy and 20% were referred based on CT imaging. All GISTs identified were located in the stomach. Out of the 69 patients identified with <2cm GISTs, surveillance was recommended in 63 (91%) and 49 (71%) had at least one surveillance EUS completed. Of the 14 patients in which surveillance was recommended but not completed, the barrier to surveillance was not identified. Over the time period of the review, there was an improvement in adherence to surveillance, reaching 100%. During a median follow-up of 12 months (range 12–24 months), all 49 GISTs remained unchanged in size and none were referred for surgery. St. Paul’s endosonographers recommendations for surveillance of small GISTs agreed with current guidelines in 91% of patients and improved over the time period of the study to 100%. There was no progression of GISTs in this cohort but a larger study is required to determine whether surveillance intervals can be increased for patients with small GISTs that have been stable over serial examinations. None

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