Might be time to get a third opinion. Since the cancer involves two organs, I would be concerned of the possibility of more spreading of the cancer when stopping the Keytruda. I agree with jaxfl. If a ctDNA test is done, that in itself may indicate that the treatment needs to continue.

The proactive thing to do would be the removal of the bladder and the prostate. With my cancer, there was not an option to try ro save my bladder. It was too invasive to take a chance. Hearing from a third set of eyes may help.