A randomized phase II/III study of paclitaxel/carboplatin/metformin versus paclitaxel/carboplatin/placebo as initial therapy for measurable stage III or IVA, stage IVB, or recurrent endometrial cancer: An NRG oncology/GOG study

INTRODUCTION: We evaluated the efficacy of the addition of the anti-diabetic drug metformin to standard-of-care paclitaxel and carboplatin (PC) in patients with advanced and recurrent endometrial cancer (EC). METHODS: In this phase II/III trial, EC patients with chemotherapy-naïve stage III/IVA (with measurable disease) and stage IVB or recurrent (with or without measurable disease) disease were randomly assigned to PC/metformin (850 mg BID) versus PC/placebo. Metformin or placebo was continued as maintenance therapy after completion of PC until disease progression. The primary endpoint of phase II was progression-free survival (PFS). The primary endpoint of phase III was overall survival (OS). Secondary endpoints were objective response, duration of response, and toxicity. RESULTS: From 3/17/2014 to 12/22/2017, 448 patients were randomized to phase II/III studies, and the data were frozen for interim analysis. The phase II study deemed metformin worthy of further investigation in the phase III study. The interim phase III analysis stopped accrual for futility on 2/1/2018. The addition of metformin to PC had a slightly higher hazard of death compared to the PC regimen (HR = 1.088; 90% CI 0.803 to 1.475), which was sufficient to close the study early. The PFS had (HR = 0.814; 90% CI 0.635 to 1.043). At a median follow-up of 10 months and 121 deaths, median OS was not determined and 28 months, on PC/placebo and PC/metformin, respectively. CONCLUSION: The hazard ratios for PFS and OS endpoints was not sufficiently decreased with the addition of metformin to PC to justify continuing the trial.