1428PRISK FACTORS AND FEATURES OF RECURRENCE AFTER CURATIVE RESECTION OF GASTROINTESTINAL STROMAL TUMOR: RESULTS OF THE KINKI GIST REGISTRY STUDY

ABSTRACT Aim: To develop the optimal method of postoperative adjuvant therapy for gastrointestinal stromal tumor (GIST), it is necessary to estimate the risk of recurrence and to predict the prognosis after resection. Methods: Patients histologically diagnosed as GIST between Jan 2002 and Dec 2007 were enrolled into the GIST registry study by the Kinki GIST study group. A total of 570 patients in 40 institutiions who underwent curative resection of the tumor and were not given adjuvant therapy were investigated in this study. The prognostic factors and features of recurrence were assessed. And the patients were stratified by the modified-Flecher's (m-F) risk classification and validated for predicting the recurrence. Results: 73 patients developed tumor recurrences. 5-year overall survival (OS) and disease-specific recurrence-free survival (RFS) were 89.8%, 86.0%, and 10-year OS and RFS were 73.1%, 72.5%, respectively. The independent risk factors for recurrence were non-gastric location (HR: 2.63, 95%CI: 1.49-4.65), tumor size >5cm (HR: 3.70, 95%CI: 1.96-7.04), mitotic index (MI) >5/50HPF (HR: 5.49, 95%CI: 3.40-10.0), presence of tumor rupture (HR:3.90, 95%CI: 1.72-8.85). The median period of recurrence after resection was 541 (range 34-3128) days and 67% of the recurrence occurred within 2 years, 86% within 3 years, 95% within 5 years. Patients with high mitotic count or with tumor rupture developed signifcantly earlier recurrece (MI >5 vs. Conclusions: Modified-F classification discriminates the risk of recurrence of GIST properly. Patients classified as high risk by m-F criteria should be given adjuvant therpy. The high MI or tumor rupture are at particularly high risk of recurrence, thus, intensive precaution should be considered for the patients meeting these criteria. Disclosure: All authors have declared no conflicts of interest.