David

The reason you "don't understand" is that my RO agrees with you that IMPT would probably deliver the least damage. But so far none of his referrals for IMPT have been accepted if the patient already had two rounds of radiation. I've been researching the heck out of this after yesterday and so far the only IMPT center I could find regularly accepting re-radiation was in Geneva, Switzerland and even they would only accept one prior radiation. Abraham cancer center has a clinical trial for IMPT re-radiation but again seems to be only for one prior radiation.(NCT01126476) I did find an interviews with MD Anderson on why they prefer pediatric or brain cancer patients and even for those they reject some. [quote]Yeah, perfect patient would be generally at this point would be benign tumors and there's a reason for that is the advantage of proton is the dose falls off so rapidly and that's a good thing. You are decreasing the amount of radiation to the surrounding brain, but benign tumors are very sharply demarcated. There's not tumor cells extended beyond them, so that's why protons works well for those. We'd mentioned earlier glioblastoma, we don't treat those tumors with protons and there's reason for that, there have tumor cells that's spread out from them and that's way kind of lose the advantage of that sharp border with protons compared to the standard photon radiation therapy.
[/quote] full podcast Best tumors for proton
The practical problem is that since proton facilities can cost up to $225 million for each one, and the ones open are still in Phase I and Phase II trials to establish that in practice IMPT is as good as in theory and better than IMRT for non brain cancers such as prostate and head/neck, it would be counterproductive for any of them to treat an extremely high risk cohort such as patients with two full prior radiation treatments. There are already a number of articles, blogs etc all citing the lack of "proof" for IMPT.
You are right that I am lucky to have an RO who has already tried to get IMPT for third time patients unsuccessfully so is willing to work with what is available.
charm