INS and urinary bladder carcinoma: However, this study had limitations inherent to its case-control design, and was underpowered with the very small numbers of diabetic patients both in the case group with bladder cancer (diabetic patients: n = 66, those treated with insulin: n = 7) and in the control group without bladder cancer (diabetic patients: n = 25, those treated with insulin: n = 7).