Imatinib therapy after resection of high-risk gastrointestinal stromal tumors in Chinese patients: a median follow-up of 48 months.

Purpose: Adjuvant imatinib can be given for gastrointestinal stromal tumors (GISTs), but adequate risk stratification is necessary to select patients who will benefit from this therapy. We aimed to investigate the treatment methods and prognostic factors of high risk GISTs. Methods: This retrospective study included 108 patients who underwent tumor resection for high-risk GISTs between January 2003 and February 2017. The patients were divided into two groups: a group of patients received postoperative imatinib adjuvant therapy (Adjuvant therapy group), and the other group was not treated with imatinib until they were found to have disease progression (Followup observation group). The progression-free survival (PFS) and overall survival (OS) were compared between the two groups, and the risk factors of prognosis were analyzed by Cox regression model. Results: The median PFS was 45 months (range 23-67). The 1-, 3-, and 5-year PFS was 88.6, 70.4 and 59.0%, respectively. The PFS in the adjuvant therapy group was longer than in the follow-up observation group (p<0.001). The median OS was 117 months (range 93-141). The 1-, 3-, and 5-year OS was 97.0, 87.7 and 77.4%, respectively. There was no difference in OS between the two groups (p=0.737). Intra-operative tumor integrity (p=0.003) and postoperative adjuvant treatment (p<0.001) were independent prognostic factors of PFS. R0 resection (p=0.019) and low mitotic count (<= 5/50 HPF) (p=0.031) were independent prognostic factors of OS. Conclusions: Avoiding intra-operative tumor rupture and administering postoperative adjuvant imatinib treatment improved PFS in patients with high-risk GISTs. Low mitotic count and R0 resection were associated with better survival.