Here are a few things you can show him. They are all about
primary radiation treatment. While salvage radiation will usually have worse outcomes than primary radiation, there is no reason to believe that the temporal pattern for emergence of side effects will be any different.
The ProtecT clinical trial was the first to randomize patients to either active surveillance or therapy and watch them over many years. It provides the first and best data we have about
the temporal pattern of the emergence of side effects relative to a randomly matched control who did not have treatment./pcnrv.blogspot.com/2016/09/patient-reported-outcomes-from-protect.html
But I do agree that if you wait long enough, urinary, rectal and sexual outcomes will deteriorate. That's because of the natural deterioration in those functions with age, regardless of any radiation treatment. The average age of men undergoing radiation is 70, so if he wants to wait 10 years, they will be 80. It would be silly to blame the deterioration on radiation when age is a well-known culprit.
In 80-84 yo men who have not had radiation or any other treatment, 82% suffer from some urinary incontinence. Among men 75 or older, 45% will have suffered loss of erectile function irrespective of any treatment.
In the following, the researchers made an attempt to separate the effect of age from the effect of radiation on erectile function after brachytherapy. They found that after 9 months whatever effect on erectile function that is going to happen has happened:/pcnrv.blogspot.com/2016/08/half-of-long-term-erectile-function-ef.html
For both SBRT and IMRT given as primary therapy, 10-year functional outcomes are similar and low:
Late-term urinary and rectal side effects were infrequent and mild in both studies:
Late-term urinary side effects:
Grade 2: 9%, Grade 3: 3% in the Katz study
Grade 2: 9%, Grade 3: 5% in the MSK study
Late-term rectal side effects:
Grade 2: 4%, Grade 3: 0% in the Katz study
Grade 2: 2%, Grade 3: 1% in the MSK study
Of those who were previously potent before radiation, 56% were potent (sufficient for intercourse) 10 years later (median age 79) in both studies.
It's pretty clear by now that anything that is ever going to happen because of the radiation therapy will have happened within the first couple of years.