In a preclinical study, it was suggested that metformin induces apoptosis and inhibits cell proliferation in cell models of endometrial cancer, especially in those with KRAS mutations.27 A recent analysis of a phase 2 clinical trial that evaluated the use of metformin associated with chemotherapy in advanced lung cancer showed that patients with mutated KRAS had better PFS and OS.16 However, in our study, patients with a RAS mutation had poorer OS than wild-type patients. The gene discussed is KRAS; the disease is lung carcinoma.