One thing my Uroligist never told me was dairy products raise the PSA levels. Also, having sex before a PSA test, even a day or two will raise the PSA level. I turn 70 Sunday, and older men have higher PSA levels. I had a PSA test done last Tuesday, had lowered my milk and cheese intake a month before, and didn't have sex for three days before. I really like milk and other dairy products. My previous test in October, when I was still drinking a gallon of milk every three days and my wife was frisky the same morning I had the test, my PSA was 7.18, I got the results from last weeks PSA after cutting down to a glass of milk every three days, and it had dropped to 6.17.
If at a point, my PSA goes above 8, I will go the route of radiation before removal, or if the Urologist feels a tumor with his didgital exam. At this point, he has never felt a tumor.
The biopsy results with let you know how concerned you need to be, and regardless of outcome of type of cancer, you will need to get a body scan to make sure it hasn't spread and your lymph nodes are still clear.
I probably would be more concerned if I was 55 or younger. I have a friend in his mid eighties who has monitored his prostate cancer for over 20 years. Again, depending on the type of cancer, plenty of things will get you in your 80's before a cancer that is not considered aagressive.
I still remember going in for the body scan and the technician asking me "So, you have cancer?" I just said, that's what they say!" although his statement question did kind of freak me out a little.
Outside of a lttle arthritus here and there, I am still in otherwise good shape for nearly 70, and still run, actually have began to enjoy running, and usually do going from my car to a big box store, just because I can. I enjoy people watching and wondering if that old fart is trying to kill himself.
I hope you have good success in getting rid of the back pain. I had sciatica in my mid 30's when surgeries on the spine did not have a good success rate, but it turned out a disc had leaked and was inflaming the sciatic nerve, flat on my back for two weeks and it healed fine, and I learned how to lift correctly and just say "no" if someone asked me to help lift something extra heavy or I would be lifting from an awkward position, like puting a water heater into an elevated closet.
God bless you.