Diagnosis and initial evaluation of patients with gastrointestinal stromal tumor (GIST): An observational study of 1,226 patients.

Abstract

10088 Background: The GIST registry (reGISTry) is an observational database designed to determine diagnostic method and evaluation of GIST patients outside of clinical trials. We previously described differences in treatment of patients in community versus academic centers (Pisters, Ann Oncol 2011;22:2523-9). Herein we present distinct differences in the diagnosis and initial evaluation of patients with GIST. Methods: The analysis cutoff date was May 2010. Patient demographics, presenting symptoms, diagnostic methodology, and KIT and PDFGRA mutations were described. For localized tumors, size and mitotic index (MI) were collected. Results: 1226 patients were included in this analysis. Initial diagnosis was most commonly made by surgeons (54.6%) and gastroenterologists (15.7%). Primary management decisions were made at time of diagnosis by medical oncologists (53%) and surgeons (53%) (sum >100% due to ≥1 responses/site). 84% were symptomatic at diagnosis, while 16% were diagnosed incidentally. Diagnostic procedure was performed during surgery (75%) and/or by endoscopy (22%) or interventional radiology (11%) using percutaneous core biopsy or fine needle aspirate. Initial diagnostic imaging was by CT scan (76%), endoscopy (25%), ultrasound (12%), or a combination. Most primary GISTs were located in the stomach (55%) or small intestine (28%). At diagnosis, localized and metastatic disease was seen in 83% and 17% of patients, respectively, with metastases mainly in the liver (62%) and/or peritoneum (36%). KIT immunostaining was performed in 93% of patients, with 98% positive. Mutation analysis was carried out in 8% of cases (57% KIT exon 11 and 12% exon 9 mutations). Of localized primary tumors, 52% were >5 cm in size and 23% had >5 mitoses per 50 high-power fields. Conclusions: We found that initial diagnosis is made by several different modalities. The majority of GIST patients are managed by medical and surgical oncologists. Most patients with localized tumor were at intermediate risk of recurrence and would be considered for adjuvant imatinib therapy.