Solid organ transplant recipients (SOTRs) in the United States have lower risks for breast and prostate cancers than the general population. To explore whether pretransplant screening explains this observation, we conducted a case-control study of US adults aged 65 years or older using the SEER-Medicare database (2000-2019). We included 252 279 breast cancer cases, 3 855 275 female controls, 316 981 prostate cancer cases, and 2 361 846 male controls. We used Medicare claims to identify solid organ transplant procedures and screening with mammography or prostate-specific antigen testing before case/control selection. SOTRs exhibited reduced risks for breast cancer (adjusted odds ratio = 0.60, 95% CI = 0.45 to 0.80) and prostate cancer (0.84, 95% CI = 0.71 to 1.00). These inverse associations were significant among screened individuals, although a borderline association for breast cancer was suggested in unscreened women. Pretransplant cancer screening probably largely explains the reduced risks of breast and prostate cancer among US SOTRs, but there may also be other protective factors.
© The Author(s) 2025. Published by Oxford University Press.