A Randomized Phase 2 Study Of Nivolumab Monotherapy Versus Nivolumab Combined With Ipilimumab In Patients With Metastatic Or Unresectable Gastrointestinal Stromal Tumor (Gist).

55Background: The therapy with tyrosine kinase inhibitors changed the prognosis of patients with advanced GIST. Unfortunately, most of the tumors become resistant to therapy and patients succumb to the disease. New therapies for this patient population are needed. Here we report interim analyses of safety and efficacy in advanced GIST patients treated with immunotherapy. Methods: Patients with advanced/metastatic GIST progressing on at least imatinib were enrolled on a randomized, parallel group, unblinded phase 2 trial of either nivolumab(nivo) (240 mg Q2wks) or nivo (240 mg Q2wks) with ipilimumab(ipi) (1mg/kg Q6wks) for up to 2 years. The primary endpoint was the objective response rate (ORR) of nivo alone or nivo + ipi by RECIST 1.1 criteria. Patients were randomized 1:1 and the response was assessed every 8 weeks. With a sample size of 20 per group, an exact binomial test with a nominal 0.050 one-sided significance level will have 82% power to detect the difference between the null hypothesis response...