I just had Proton Therapy at UFHPTI in Jacksonville. While there, a couple of guys came by for their 9 and 10 year checkups. Both had no issues. You should call Loma Linda and speak to their Urologist/Oncologist about this. The one thing we were cautioned about was to have any urologist contact the Proton Therapy doctors before probing around in rectums or urethras. Also, you've gone 15 years without problems and I doubt the kidney stone is the fault of proton therapy, but I would give Loma Linda a call. They were the pioneers in Proton Therapy.