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PSMA PET Scans...some interesting info
Prostate Cancer | Last Active: Oct 28 4:54am | Replies (67)Comment receiving replies
@heavyphil As it turns out, PSMA (prostate specific membrane antigen) is not really “prostate specific.” There are other organs, tissues, and fluids that naturally express PSMA (without being cancerous) and will show as avid physiologic tracer uptake on a PSMA PET scan - particularly in the lacrimal (tear) and parotid (salivary) glands, blood, liver, spleen, pancreas, ganglia, and more, as well as the kidneys, ureters and the bladder (as the body tries to quickly excrete the radioligand that was injected).
So, I wouldn’t consider it “subjective”, but as taking a very well-trained eye, as well as using results from other diagnostics in order to make a determination.
As for whether a PSMA PET scan would show a discernible SUV increase in a lymph gland at a 3 month interval would depend on the aggressiveness of the cancer. If the PSA was low, perhaps not; if the SUVmax was less than the SUVmax of blood, also perhaps not.
A high PSA Velocity could be from a lesion anywhere in the body, thus the PSMA PET scan to try to find where.
As for necessary treatment, that’s where Dr. Kwon’s statement comes into the picture again —> “…. only 1/3 of men who have recurrence following prostatectomy have recurrence only in the prostate bed; they should not get salvage radiation there unless they’re absolutely certain of the location of recurrence; first confirm where the recurrence is.”
Replies to "@heavyphil As it turns out, PSMA (prostate specific membrane antigen) is not really “prostate specific.” There..."
@brianjarvis Thank you, Brian, for the link to Dr Kwon’s presentation. I like his speaking style so much more than many of the other experts.
But here’s the one thing I don’t get - and probably it’s MY fault for not getting it - but he says we always want to treat earlier rather than later; great, I agree…
…but then he makes that statement about NOT treating anything until you can see it, since only about 30% of men have recurrence in the prostate bed…Huh?? He just said to treat it early, ideally < 0.2…
I went back and reviewed my own PSMA: clear with no sign of activity ANYWHERE - not even in the ‘focal bed’, yet my PSA of O.18 prompted treatment.
Don’t get me wrong, my PSA was rising - but slowly and inconsistently over a period of about 18 months; NOT on a pace where PSA velocity was even an issue. It was more like: only PCa would cause a consistent rise in PSA over time, not ‘normal’ tissue left behind from surgery…who really knows, right?
Anyway, I had 25 radiation treatments to the bed+ pelvic nodes and 6 months ADT and am now undetectable.
But isn’t Dr Kwon saying that I should not have done anything? I should have waited for bright lights on my PET since nothing was visible? Wouldn’t that be too late rather than too early IF I was one of those men in the 30% whose recurrence was still confined to the prostate bed?
@jeffmarc has mentioned Dr Kwon’s preference for SBRT on visible lesions (over SRT on invisible ones) many times - and Dr Kwon illustrates this treatment with a few actual cases he’s successfully treated using this approach.
But what I think would be more telling, is how many cases slipped thru the cracks and became widely metastatic during the interval where lesions were invisible and then when they lit up like a Christmas Tree…? Nobody bats 1,000 pct- not even Dr Kwon and unless I am interpreting what he is saying incorrectly, his approach sounds like a bit of Russian roulette to me…
I have no regrets whatsoever that I opted for SRT - even in light of a negative PSMA. My PSA could still be rising to levels portending an unfavorable outcome (>0.7) and my PSMA could STILL be negative…How can you wait?? Best,
Phil
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@brianjarvis Just so. We discovered my prostate cancer via the lesion on my spine. There was no evidence of local spread in imaging (MRI, CT contrast, bone scan) and not even anything visible in the prostate itself. The cancer seems just to have taken off out of the nest (prostate) almost as soon as it was hatched and settled in my middle spine.