I was lucky enough to be recommended by Darryl and Malecare (thank you for that) to participate as a "consumer reviewer" for the "Department of Defense, Congressionally Directed Medical Research Programs, Prostate Cancer Research Program". There were about 15 scientists, mainly professors of medicine or molecular biology, and two of us prostate cancer survivors who were there to provide a patient point of view.
It was a fascinating experience that, unfortunately, I can't talk too much about because we were reviewing proprietary proposals by various labs looking for government research funds and we all had to agree to confidentiality provisions that forbid us from saying anything at all about the research proposals we read. However, on the side, at meal times, I asked various scientists for their views on subjects of interest to patients. One question that I asked of two different medical school professors of radiation oncology was, Is proton beam therapy better than x-ray therapy for prostate cancer treatment? I asked the question at two different meals, one with each of the professors, so they didn't hear each other's answers. They were from different universities, but their answers were pretty similar.
I didn't say to the professors that I was planning to publish their statements (and in fact I had no specific plans yet about that) so I don't feel that I have the right to use their names. All I will say is that there were two of them, they were medical school professors and radiation oncologists who are recognized in the field of prostate cancer research, they answered my questions without hearing each other's answers, and I'm giving you what I believe to be an honest and accurate report of what they said.
First of all, both of them said that there is no difference in outcomes. As one professor put it, assuming that the beams are properly aimed, the success of radiation therapy is entirely dependent on the dose administered and it doesn't matter whether the dose is of protons or of x-rays. He said that the dosage levels matter, type of radiation doesn't. Your chance of killing off the cancer is the same with x-rays or with protons.
The other question I asked was, are the side effects different. One professor answered this way: He said that, theoretically, there are reasons for believing that the adverse side effects from proton beam will be less than for x-rays. However, he said, there are no good studies that compare them and we really don't know if the side effects are better.
The other professor answered differently. He also said that there are no studies giving objective evidence, but he doubted that the side effects of proton beam were any better than for x-rays. His reasoning was as follows:
The most sensitive tissues in which "late complications" occur are in the rectal wall and the bladder neck. He drew me a diagram to show that the rectal wall is smack dab up against the back side of the prostate, and the bladder neck is right up against the top of the prostate. He said that, because of their close proximity, there is no way to spare the rectal wall or the bladder neck without also sparing the part of the prostate itself that is up against those other tissues. He therefore thought that proton beam would only spare the rectal wall and the bladder neck if it didn't treat the entire prostate - which risks a worse outcome in killing all the cancer.
I told one of the doctors that I knew a man some years ago whose insurance would not cover proton beam so the man mortgaged his house to raise the $70K to pay for it. The doc was horrified.
Are the two professors right? I'm not qualified to say. However if they are right, then I think the lesson to be learned is: Find the best radiation oncologist - the one who is going to aim the beams or the seeds carefully and right and who is going to give the right dose. The choice of protons vs. photons (x-rays) is irrelevant.
I believe that there has been a lot of hype and a fair amount of advertising puffery by some proton beam therapy centers. One center in the Czech Republic is even advertising a 98% "cure" rate, which I think is a ridiculous and pernicious statement.
For whatever they are worth those are my thoughts on the matter.