I'm sure you're already very familar with the VA's procedures regarding treatment/compensation for radiation issues resulting from possibly service-connected exposure.
But as an information item for others reading this thread who aren't, and who may want to know more of the details:https://www.publichealth.va.gov/exposures/radiation/benefits/index.asp
It's too bad there isn't a presumptive condition clause for radiation, as is the case. for example, with veterans who served in Vietnam and later developed PCa.
But keep trying with the VA. It often does happen that if a veteran just works at it long enough, the VA eventually comes around, sees things his way, and the benefits start.
I know of at least one Navy vet right here on this forum for whom that turned out to be the case. He just kept working through the denials, and eventually got a 100% disability rating as I recall.
Chronic prostatitis (age 60 on)
BPH w/ urinary obstruction, 6/2011
Ongoing high PSA, 7/2011-12/2011
Biopsy, 12/2011: positive 3/12 (90%, 70%, 5%)
Gleason 6(3+3), T1c
No mets, PCa likely still organ contained
IMRT w/ HT (Lupron), 4/2012-6/2012
PSAs (since post-IMRT): 0.1 or lower