Male kids before me, also had to do a surgery to remove something from their testes to make sure that there wasn't any chance of having the repository for the cancer left. I was lucky enough to not have to do that.
I do find it impressive though that this is still a thing as I was treated many years ago. My feeling was always that the treatment protocols, for ALL at least, tend to get more aggressive but also much shorter. Exactly because of the tradeoffs you mentioned.
Your little one is a hero. He might be too young right now to realize what he has achieved but please keep reminding him that.
Also, something that I don't see being discussed enough when it comes to childhood cancers, is the effect it has to the family as a whole. Parents especially, do come out with their own trauma from this experience and they need to heal too.
Finally, for anyone interested.
Stanford has an amazing Adolescent and Young Adult Cancer program (SAYAC)[1], hopefully more institutions have similar programs but I can't emphasize enough the value they can bring.
Elephants and Tea [2] is a magazine for adolescent and young adult (AYA) patients, survivors, and caregivers. Great place to learn more about the experiences from the people who are there or have been there.
1. https://www.stanfordchildrens.org/en/services/adolescent-you... 2. https://elephantsandtea.org