We still seem to be marching along together in step with our radiation treatments. I finished my 15th of 40 proton treatments today. You and I will make an interesting comparison during treatment and after (i.e., IMRT x-ray for you and proton for me). I still have some urinary and bowel side effects, but nothing that I can't deal with--Flomax, Advil and Metamucil help.
In answer to your question, they have to radiate the entire prostate to make sure that they get all of the cancer contained therein. As you probably know, the biopsy is limited to samples of the prostate and certainly cannot be relied on to detect exactly where all of the cancer lies in the prostate. This is often confirmed when patients have surgery and find that their post operation pathology is worse than the biopsy predicted. Lastly, the prostate is not a very large organ and I doubt that they could direct the radiation just to specific areas of the prostate even if they could accurately pinpoint the cancerous areas.
Try not to think about potential ED--just enjoy what you have right now. Moreover, viagra and other similar pills help those who have had radiation to overcome ED if it appears months or years later after radiation. There is no guarantee, but I think that radiation patients have a greater chance for achieving potency with pills than those that choose surgery.
Continued good luck buddy!
68, Biopsy 9/27/06, Stage T1c, PSA 7.1, Gleason 6 [less than 5% in two areas], Gleason 7 (3+4) [less than 20% in third area], negative DRE, bone scan and MRI. Starting proton radiation therapy 2/22/07.