Testosterone therapy and cancer risks among men in the SEER-Medicare linked database

Background We examined associations between two forms of testosterone therapy (TT) and risks of seven cancers among men. Methods SEER-Medicare combines cancer registry data from the Surveillance, Epidemiology, and End Results programme with Medicare claims. Our population-based case–control study included incident cancer cases diagnosed between 1992–2015: prostate ( n = 130,713), lung ( n = 105,466), colorectal ( n = 56,433), bladder ( n = 38,873), non-Hodgkin lymphoma ( n = 17,854), melanoma ( n = 14,241), and oesophageal ( n = 9116). We selected 100,000 controls from a 5% random sample of Medicare beneficiaries and used logistic regression to estimate odds ratios (OR) and 95% confidence intervals (CI). Results TT was associated with lower risk of distant-stage prostate cancer (injection/implantation OR = 0.72, 95% CI: 0.60–0.86; topical OR = 0.50, 95% CI: 0.24–1.03). We also observed inverse associations for distant-stage colorectal cancer (injection/implantation OR = 0.75, 95% CI: 0.62–0.90; topical OR = 0.11, 95% CI: 0.05–0.24). Risks of distant-stage colorectal and prostate cancers decreased with time after initiating TT by injection/implantation. By contrast, TT was positively associated with distant-stage melanoma (injection/implantation OR = 1.70, 95% CI: 1.37–2.11). TT was not associated with bladder cancer, oesophageal cancer, lung cancer or non-Hodgkin lymphoma. Conclusion TT was inversely associated with distant-stage prostate and colorectal cancers but was positively associated with distant-stage melanoma. These observations may suggest an aetiologic role for TT or the presence of residual confounding.