Long story short. I have Had prostate cancer 10 years now. When we first fond it I had my prostate removed. My PSA was only 6. A little over 5 years went by and my PSA started going up. When now I was in stage 4. I had a tumor where my prostate was and it was in my bones. By the time if finished radiation and started hormone therapy my PSA was only 7.85. We got back to .01 but as the years went by my PSA went back up to 7.9. We did immunotherapy and spot radiation and brought it back to 2.0. It is climbing again and I'm at 4.8. Waiting to start new treatments.
Anyway the point is my PSA has never been above 7.9 but over the years we have learned that once it stats claiming 4.0 is the magic number to start looking where it is and what it is doing.
You need to learn your numbers and what they mean to you. All of us are different and your numbers mean different things to each of us. My dads magic number is 1000. So there is a big difference. Set your baseline early. If used properly PSA can be very helpful to know where you are at and what is going on in your body.