Mike ~
I apologize for the misunderstanding.
You're right, it's definitely a question for the doctor. I received 27 Gy of radiation (via FSR) but was 63 at the time and did not have a history of receiving much radiation until that time. The effects of irradiation (under medical supervision) are not perfectly understood but the move seems to be away from the old beliefs that radiation treatment is only for those over 60. My radiation oncologist was very exact and informed me that I would receive the absolute minimum 'dose' of radiation - very specifically targeted - that would still be effective. I suffered no side effects and the FSR did it's job of destroying my remaining remaining tumor's DNA and thus, it's ability to re-grow. Mission accomplished!
Six years later, I'm fine and I doubt the radiation had any long-term negative effect on me. However, this is anecdotal and not 'scientific' proof of anything. Again, we can speculate but your doctor should be your most credible source of information on this important issue.
Jim