What's the current thinking on Proton for SRT?

Proton is effective for small tumors in hard to reach places. SRT involves a wide area and other forms of external radiation are much less expensive and better suited to SRT. Think of needing a shotgun rather than a rifle for SRT.

Sorry to hear about your rise in PSA. I would have bet after 4 years you were in the clear.

When I was being treated in Jacksonville at UFPTI in January this year, there were several men being treated with proton after surgery had failed. I do not know the particulars of their cases. John T may be right in saying IMRT is better at SRT than proton. When I was being evaluated it was thought I might have SV invasion. Fortunately, a biopsy of the SV was negative but I still had 2cm of the SV treated. My RO said if the biopsy had been positive, I would have had 4 weeks of IMRT, followed by 4 weeks of proton. The IMRT, he said, would cover the pelvic area including lymph nodes.

There are a number of insurance companies that do not cover proton. The reason, I think, is not because it's experimental, but that it's more expensive than IMRT and has not been proven to be more effective for a cure. Fewer side effects have been shown with proton in several studies, but my guess is the insurance companies are not willing to pay for fewer side effects.

I have a friend who received proton as part of a SRT plan that also included IMRT. As others have noted, the proton was used to treat some specific spots, while the IMRT was used to treat a much larger "shotgun" approach area.