@neilmartin
I am not a medical professional and neither a research specialist medical professional either. But have gone through proton radiation like your did without any hormone treatments. I also have had 2.5 years of follow up PSA tests.

Here is my experience and what I learned directly from my urologist, R/Os and PCP. When you have proton radiation it is to damage your cancer cells. It also damages our regular prostate cells. The difference is that your cancer cells cannot repair themselves and eventually die. That is why the long term time frame from getting your lowest PSA. Your prostate cells can repair themselves and will eventually do. Remember though your prostate has gone through WWIII.

So it takes time for all the cancer cells to die over time. It is why the long term PSA numbers don't usually get to their lowest point for several years. You should have been told that bumps in your PSA (up/down) are normal and common but not usually the extent yours did.

Some things I did not see posters asked you. Did you use the same lab for all your PSA tests. This is important as results can be different at different labs and different equipment.

Did you have BPH before you proton radiation? It is hard to distinguish a rise in PSA caused by BPH and a spike of PSA coming from a rising cancer cells. Do you have any signs of prostate infection or UTI. Again after prostate radiation hard to tell if side affects are radiation or BPH, infections, irritations which will cause a rise in PSA numbers as well. These issues can cause quite a rise in PSA and it not be related to cancer.

Your initial of 10 PSA to 6 at 3 months (are you having them done every three months) is good. Then a spike then down again then up again to original point the first test after treatment. Really troublesome but can't rule out infections, BPH, and UFIs either. I would highly recommend your urologist looking at any sign of BPH, infections, and UTIs.

Your questions should be answered by your urologist, R/Os, oncologist as they are the medical experts to determine what is happening here and what is causing the dramatic up and down numbers. Most of the time the numbers go down with an occasionally spike. The R/Os look for sustained ups as a concern but yours are not doing that but bouncing all around.

Did you not have a PSMA done originally? That is a test most of us on MCC suggest and quite normal part of diagnosis for applicable treatments. Your decipher test was low risk was that correct. So unless your biopsies did not catch an area that had a higher area of cancer (which can happen) your cancer should have been slow growing.

Asked your oncologist and R/O did they treat your entire prostate or only the areas identified on biopsies. If they did not treat entire prostate could have missed areas with cancer and thus growing. It is why most (can't say all) that get the traditionally x-ray treatments have the entire prostate treated.

I see many times new types of radiation treatments to only radiate the specific areas identified as having cancer. With prostate cancer cells many times at cellular level would be easy to miss them as you can't take a biopsy of every cell of prostate.

That Decipher test has changed a lot of those on MCC to a higher risk that their Gleason Score did and in my case a lower risk.