P-192 Cytoreductive surgery in patients with metastatic gastrointestinal stromal tumors sensitive to imatinib: A retrospective analysis of 2 Russian cancer centers

Abstract

The role of cytoreductive surgery for patients with metastatic gastrointestinal stromal tumors (mGIST) responding to imatinib (IM) has not been established yet. There are no results of randomized clinical trials to assess whether surgery to treat residual disease improved progression free survival (PFS) compared with IM treatment alone. We carried out a retrospective analysis of the outcome of patients with mGIST and compared two cohorts: treated or not treated with surgery after partial response or stable disease on IM. A total 44 patients treated by IM as first-line treatment were included in our analysis. To compare prognostically similar patients only sensitive to IM cases with hepatic or peritoneal metastases were analyzed as a control arm. The efficacy was evaluated on CT according to RECIST 1.1. Patients were divided into two cohorts: treated with IM only and not treated with surgery – NS group, n=29 and treated with IM and surgery – S group, n=15. Patients in the NS group received only IM until disease progression. Patients in the S group were treated additionally with metastasectomy after having response or stable disease on IM with further treatment with IM until disease progression. The baseline characteristics were similar between the groups with were several trends: higher proportion in S group achieved partial response (86 vs. 56%, p=0.165), and great number of patients in the NS group had peritoneal metastases (45 vs. 27%, p = 0.759). Median time to surgery from the initiation of IM was 8 months (range 3-23 months). Complete resection was achieved in 13/15 (87%) and incomplete resection - 2/15 (13%). PFS was significantly longer in the S group compared with the NS group: median PFS were 78 vs. 35 months. The PFS curve showed a trend towards survival benefit in the S group without statistically significant improvement (р=0.08). Surgical resection of residual lesions after disease control with IM is likely to be beneficial to patients with mGIST.