I can't think of anything I changed in my diet as a result of prostate cancer (ignoring temporary changes like going fibre-free during radiotherapy, and higher percentage of protein during hormone therapy).
I've never drunk alcohol, but that's just because I never found one I particularly liked.
I stopped eating beef during BSE and never really took it up again, but I never was a great fan of it. I'll allow myself a few good quality hamburgers at summer BBQs, and perhaps a really good steak and kidney pie in a restaurant probably less than once a year.
I stopped eating red meats and processed/preserved meats 2-3 decades ago, recognising they're a very significant cause of bowel cancer.
I'll eat any of these things if they're what's provided when at a friends, but they're things I don't buy for myself.
I still have plenty of dairy. I mostly don't achieve my 5 a day, and I still do Pomi-T on the basis it might compensate and might help prevent recurrence. Many days I have no meat, and what meat I have is mainly chicken and fish.