Yet another update on this confounding PSA journey.

Just got yesterday’s (May 20) PSA test result back—0.100.

If you calculate the average of my two previous post-salvage RT values (0.086 and 0.113), it comes to 0.100.

From the three post-RT values to date, it seems that my PSA really isn’t budging one way other the other. Recall that going into RT my PSA was 0.094, and 3 months before that, at the first suspicion of a relapse, my PSA was 0.11 (standard Quest test, not Labcorp ultra sensitive test). My PSA seems to be stuck at 0.1 with a variance of 0.013.

Will be discussing the new result with my RO soon.

The question in my mind is, why has my PSA not dropped following RT and seems to be “stuck”? I have three hypotheses regarding that.

1 - the tumor in my prostate bed consists of indolent cancer. If the cancer is non-aggressive, then the cells are not dividing rapidly. If they are not dividing all that much, then they are not dying from the radiation induced damage to the cellular DNA. This is consistent with the fact that my relapse didn’t occur until ten years after my RARP. In this scenario, I might see a gradual decline in my PSA over a few years. A PSMA PET scan probably would look similar to my initial scan from last summer.

2 - the tumor in my prostate bed was whacked by the radiation but I have a distant met or mets that are producing some PSA. At this point, they may well be micro-mets, and with my relatively low PSA, they would not be likely to show up on a PSMA PET scan. But, if the original tumor is dying off, then there might be scan evidence for that (either smaller spot or lower maximum SUV). PSA should rise over time if this is the case. This hypothesis is also consistent with my elevated ALP (discussed in original post).

3 - radiation has damaged the cancer cells in the tumor but they are able to repair the DNA before dividing. Again, sort of a steady-state condition like hypothesis 1, but over time the cancer may overcome the radiation damage and grow and spread. In this scenario, I might expect to see a rising PSA over time after a period of stasis. A PSMA PET scan now probably would show little change since last summer's scan.

So, at this point, I am not sure another PSMA PET scan would reveal anything telling. Given that there is an insurance co-pay of some $200, I am less than eager to proceed with a scan at present, unless my RO can convince me that we might learn something useful.

However, frequent PSA testing (i.e., monthly) still seems like an intelligent, and no cost, way forward for now. More data are needed over time to see if my PSA is trending up, down, or just holding steady around 0.1.

All a bit puzzling, but the good news is that I am not really looking at rising PSA…yet. And I’ve heard of several cases where it took years for PSA to bottom out following salvage radiation. Not the norm, but then my case certainly qualifies for being outside the norm.

As always, I welcome your thoughts, experiences and insights.

Mel