10043 Background: To review the morbidity of post-IM surgery of residual disease in a consecutive series of metastatic, IM- sensitive, GIST pts. Methods: Between November 2002 and September 2006, 29 pts with metastatic GIST were operated on, being progression- free on IM for at least 6 months. Median preoperative IM duration was 17 mos. Only patients deemed to be completely resectable on CT/MRI were considered for surgery. Major surgical procedures were generally excluded. Results: Surgery consisted in explorative laparotomy with resection of residual visible disease, omentectomy in 13 cases, intestinal resections in 10, minor hepatic resections in 7, radiofrequency ablations of liver nodules in 2, spleno-pancreatectomy in 2. Macroscopically complete surgery could be performed in 90% of pts. Median operative time was 180’ (range 120–420). Median post-surgery discharge time was 9 days (range 4–35). Median preoperative Hb level was 12.2 mg/dL and the median perioperative whole blood and fresh frozen plasma units required was 1.5 and 2.9 (range 0–16 and 0–44), respectively. In 28% of pts, there was post-operative ascites (daily peritoneal effusion of >200 ml), which generally responded to medical therapy in one week. Postoperative levels of AST/ALT reached twice the baseline in 48% of pts, independently of whether liver resections had been carried out. Postoperative pneumonia was observed in 38% of patients. Major surgical complications occurred in 14% (one bleeding, one evisceration, and two anastomotic leakages). After a median follow up of 36 mos from surgery, PFS was 69% at 2 yrs (65% at 4 yrs from IM-onset). Conclusions: While this was a series of favorably selected patients, and major surgical procedures were preferably avoided, surgical perioperative morbidity turned out to be higher than expected. This reinforces the view that post-IM surgery of residual disease in metastatic GIST pts should be considered investigational, as long as its efficacy in improving prognosis is not demonstrated. [Table: see text]