P-264 The effect of preoperative imatinib therapy in gastrointestinal stromal tumors: A multicenter study

Preoperative imatinib therapy has been recommended as a safe and efficient approach for unresectable local advanced gastrointestinal stromal tumors (GISTs) regardless of synchronous metastasis or not. However, whether different primary sites would impact the efficacy duration time preoperative was still under exploration. Besides, it unclear about effect on surgical outcomes prognosis. We retrospectively collected clinical data GIST patients with without metastasis, who all received surgery postoperative from 2010 to 2020 in West China Hospital, Sichuan Provincial People's Cancer Affiliated Hospital Guizhou Medical University. A total 63 (28 gastric, 14 small intestinal, 21 rectal GISTs) were analyzed group, among which 9 liver metastasis. The median treatment 8 months (range: 1-24 months) all, 1-22 gastric GIST, 9.5 (range:2-24 intestinal 6 4-10 GIST. There 42 (66.7%) partial response (PR), 19 (30.2%) stable disease (SD), 2 (3.2%) progressive (PD). None reached complete (CR). follow-up 41 (range:11-126 months). 3-year 5-year progression-free survival (PFS) group 77.2% 59.0%, overall (OS) 97.7% 89.5%, respectively. Univariate analysis showed that enteral bleeding symptoms, tumor size > 5cm after therapy, combined organ resections, complications, necrosis associated worse PFS. Multivariate confirmed only symptoms independent risk factor PFS (hazard ratio [HR]: 4.496, 95% confidence interval: 1.329-15.216, P=0.016). For metastases, could reduce by one-third nearly two-thirds patients. slight difference shrinkage rate most obvious while change not significant other sites. Meanwhile, reach plateau stage based sites, slightly longer than shortest. Gastrointestinal predicting recurrence location suggesting traditional assessment criteria may be suitable these