Phase II trial of nivolumab and metformin in patients with treatment-refractory microsatellite stable metastatic colorectal cancer ================================================================================================================================== * Mehmet Akce * Batoul Farran * Jeffrey M Switchenko * Manali Rupji * Sandra Kang * Lana Khalil * Amanda Ruggieri-Joyce * Brian Olson * Walid L Shaib * Christina Wu * Olatunji B Alese * Maria Diab * Gregory B Lesinski * Bassel F El-Rayes