Nice post Jerry.
But we really lack comparisons. That fact is that when PBT became available, we had no IMRT or IGRT. But these technologies have heavily reduce side effects. To the point where we argue which is better. I can't answer that question. Neither can the cohort of radiation oncologists.
And with the dollar differential?
The balls in their court to prove it's better.
And the proton folks are aware of this. During my time at IU Health, I had the opportunity to talk several times with the director of the facility, and among the things we discussed were the future of proton therapy and insurance coverage (he was aware of my insurance battle). There are several trials going on right now designed to hopefully demonstrate the major benefit of proton therapy for prostate patients, i.e. fewer side effects both short and long term. Informally, they will also tell you that their in-house studies show without a doubt that proton therapy has fewer side effects than photon (even with the newer photon techniques). But they recognize the clamor for "official" studies and these are now in progress. Of course, a study of long term side effects naturally takes a long time to complete, so it may be awhile before we know "for sure."
Other interesting studies that are going on now or getting ready to be undertaken is shortening the treatment time in number of days by increasing the daily dosage. Studies are being formulated to look at using 28, 20 and even 5 days (i.e. cyberknife) keeping the dosage to the prostate consistent.
It will be interesting to see how this all plays out.