SEER- and Medicare-linked database analysis indicated that T2DM patients taking a DPP-4 inhibitor had a worse trend of overall survival (OS) with HR 1.07 (95%CI: 0.93–1.25, p = 0.33) in the breast cancer cohort and HR 1.07 (95%CI: 0.93–1.24, p = 0.68) in the pancreatic cancer cohort, whereas DPP-4 inhibitor use had significant OS benefit with HR 0.77 (95%CI: 0.64–0.93, p = 0.005) in patients with prostate cancer [128]. This evidence concerns the gene DPP4 and Familial prostate cancer.