INS and lung cancer: In the analysis stratified by control group drugs, a no-drug or insulin study had a null relationship between the incidence of lung cancer and metformin in diabetic patients (RR = 0.89; 95% CI, 0.77-1.03; P = 0.13 and RR = 0.97; 95% CI, 0.75-1.26; P = 0.84, respectively).