The role of surgical resection following imatinib treatment in patients with metastatic or recurrent GIST.

Abstract

10550 Background: Several retrospective studies have suggested that surgical resection of residual lesions could be beneficial if resection was done after disease control (partial response or stable disease) with imatinib in patients with metastatic or recurrent GIST. However, the benefit of surgical resection has not been proven yet compared to imatinib alone. Therefore, we compared the outcomes of surgical resection of residual lesions after imatinib (SI group) with those of imatinib alone (IM group) in patients with metastatic or recurrent GIST controlled with imatinib treatment. Methods: A total of 134 patients with metastatic or recurrent GIST who showed at least 6 months of disease stabilization or response to imatinib were included in this retrospective analysis. Patients were categorized into SI (n=42) or IM (n=92) group. To reduce the selection bias, propensity scores and inverse-probability-weighting (IPTW) adjustment were used in the outcome analysis. Results: Patient and tumor characteristics were statistically similar between SI and IM groups, except median age (51 in SI, 58 in IM, p=0.002), and metastases to peritoneum (12 in SI, 56 in IM, p=0.001). The patients in SI group underwent surgery of residual disease after a median 19.1 months of imatinib treatment (range, 7.2-87.0). With a median follow-up of 58.9 months (range, 15.4-129.1), progression-free survival (PFS) and overall survival (OS) were significantly longer in SI group than in IM group (PFS, 87.7 vs 42.8 months, p=0,001; OS, not reached vs 88.8 months, p=0.001). Multivariate analysis revealed SI group as well as female sex, KIT exon 11 mutation, and low initial tumor burden were associated with longer PFS, and SI group and low initial tumor burden were associated with longer OS. Even after applying IPTW adjustment, SI group showed significantly better outcome in terms of PFS (hazard ratio [HR], 2.326; 95% CI, 1.034-5.236; p=0.0412) and OS (HR, 5.464; 95% CI, 1.460-20.408; p=0.0117). Conclusions: This study strongly suggests that surgical resection of the residual lesions after disease control with imatinib may be beneficial in patients with metastatic or recurrent GIST.