Your friend should do a little research on his own before his next conversation with his urologist...he can find the same journal info online that medical researchers publish for doctors. The medical community's understanding of TRT post-PC has undergone a paradigm shift; there used to be a blind fear that "testosterone might trigger some residual PC somewhere"...but general contraindication is largely debunked now and physicians also have a deeper understanding of the broader harms of hypogonadism.
But just because the new information is out there that doesn't mean every doctor is fully up-to-date. An informed patient is going to be the most satisfied with his treatments.
Here's a starting point:
- from the Renal and Urology News, 2018: "Testosterone Therapy Safe Despite Prostate Cancer History" https://www.renalandurologynews.com/aua-2018-coverage/testosterone-replacement-therapy-safe-for-prostate-cancer-patients/article/767232/
- from European Urology, 2016: "Testosterone Therapy in Men With Prostate Cancer" (by Kaplan, Hu, Mulhall, and others) https://www.europeanurology.com/article/S0302-2838(15)01213-0/fulltext