Adjuvant therapy with imatinib in gastrointestinal stromal tumor (GIST) patients with intermediate or high risk: Analysis from a single-center contrast study

Abstract

10556 Background: Imatinib benefits the patients with metastatic GIST but whether it is effective in the adjuvant setting after complete tumor resection of primary GIST is questionable. Methods: Patients who had undergone complete tumor resection with intermediate or high risk of recurrence (define) were enrolled in a single-center non-randomized open contrast study. Patients had adjuvant therapy with imatinib (400mg once a day) for 3 years commencing within 12 weeks of tumor resection, or had follow-up alone. We performed c-kit and PDGFRA mutation analysis for patients with archival tumor samples. The primary objective was recurrence-free survival (RFS) and the second objective was correlation of gene mutation profile with efficacy of adjuvant therapy. Results: One hundred and five patients were enrolled: 56 patients in adjuvant therapy group and 49 patients in control group. Median follow-up was 30 months (range 12–62); Median treatment duration in adjuvant therapy group were 20 months (range 12–36); There was relatively higher 1-year and 2-year RFS in the adjuvant therapy group compared with the control group (100% vs 89.8%,94.4% vs 60.0%) (Log-RankP< 0.001). Hazard risk was 0.13 (95% CI 0.039–0.438, P= 0.001) in Cox proportional hazard regression model. For further sub-group analysis, Log-rank and Cox regression analysis showed that adjuvant therapy could significantly decrease recurrence risk in patients with high risk disease (define)(2-year RFS: 91.5% vs 46,2%, Log-Rank: P<0.001, HR:0.107 (95%CI 0.031–0.370), P<0.001). c-kit and PDGFRA mutation were analyzed in forty-nine patients. There was a better survival benefit from adjuvant therapy for patients with c-kit exon 11 mutation. Conclusions: Adjuvant therapy with imatinib can improve 1-year and 2-year recurrence-free survival for patients with an intermediate or high risk of recurrence after complete tumor resection. No significant financial relationships to disclose.