first PSA result post salvage RT — 0.086

Here’s what they do with that SUVmax of 13.3.

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 up as 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, they use for comparison the PSMA SUVmax values of your blood (as the lowest level), liver (as the medium level), and parotid or lacrimal glands (as the highest level) of SUVmax expression.

If your suspicious area is expressing PSMA (yours is 13.3), and it has:
> a PSMA SUV score less than blood, then it’s not likely cancer, but instead just normal, background PSMA cellular expression;

> a PSMA SUV score greater than blood, but lower than liver, then it’s likely low-grade prostate cancer;

> a PSMA SUV score greater than liver, but lower than the lacrimal/parotid glands, then it’s likely moderate-grade prostate cancer;

> a PSMA SUV score greater than the parotid/lacrimal glands, then it’s likely high-grade prostate cancer;

Where does your 13.3 SUVmax fall on that blood-liver-parotid(or lacrimal) SUVmax range?

As always, discuss all this with your doctor.

@brianjarvis

Brian, Many thanks for this information. Given the discrepancy between my PSA and SUVmax, I’ve suspected that there is something being missed in reading the tea leaves of the PSMA PET data. Perhaps this is it. Neither the radiologist who issued the report, nor my urologist mentioned anything about comparing against SUVs of different organs and blood. I will certainly bring this up with my RO and urologist, both of whom I will see in the next couple of weeks.

Do you have any references for these comparisons—journal articles, conference presentations, etc? Would be useful to share those with my docs.

I doubt that the nodule is residual prostate tissue. I had regular DREs following my RARP, as well as PSA tests. In the ninth year after my RARP, my urologist first detected a lump during a DRE, but my PSA was still undetectable (< 0.1) at the time, so there was no further action. It was a year later (June 2025) when my PSA rose to 0.11 that all the alarm bells started going off. I suspect that the recurrence is low grade cancer, but it sure would be good to confirm/correct that hunch with some actual data.

@melvinw Dr. Johnson (of Mayo Clinic) talks about scans in his (hour-long) presentation, starting with the scans we’ve all heard about (MRI, bone, & CT scans), and then going into great detail about PSMA PET scans: https://youtu.be/JoJomACA5UM

@brianjarvis

Brian, Many thanks for this information. Given the discrepancy between my PSA and SUVmax, I’ve suspected that there is something being missed in reading the tea leaves of the PSMA PET data. Perhaps this is it. Neither the radiologist who issued the report, nor my urologist mentioned anything about comparing against SUVs of different organs and blood. I will certainly bring this up with my RO and urologist, both of whom I will see in the next couple of weeks.

Do you have any references for these comparisons—journal articles, conference presentations, etc? Would be useful to share those with my docs.

I doubt that the nodule is residual prostate tissue. I had regular DREs following my RARP, as well as PSA tests. In the ninth year after my RARP, my urologist first detected a lump during a DRE, but my PSA was still undetectable (< 0.1) at the time, so there was no further action. It was a year later (June 2025) when my PSA rose to 0.11 that all the alarm bells started going off. I suspect that the recurrence is low grade cancer, but it sure would be good to confirm/correct that hunch with some actual data.

@melvinw As for the discrepancy between PSA and SUVmax —> Remember that a PSA is a hard number, subject to the calibration, sensitivity, limitations, and accuracy of the lab equipment used.

On the other hand, an SUVmax score (just as with a PIRADS score and a Gleason score), is a specialist’s educated and expert “opinion” of what he (or she) believes they see in an image, scan (or under a microscope) - it’s often as much an art as it is a science.

What one pathologist sees as a Gleason 7(3+4), another might see as a 6(3+3) and another see as a 7(4+3); what one might see as a PIRADS 3, another might see as a PIRADS 2, and another as a PIRADS 4. Similarly with SUVmax scores….

Additionally, PSA is not always tied to aggressiveness of disease. So, it’s not necessarily a “missed in reading the tea leaves,”; there’s simply no way to know who is right……

@brianjarvis Yes to all that. I’ve also read that because PSMA PET scans are so new that docs are still trying to get a handle on what the data are actually telling us.

The hard facts I have in hand are: (1) it was nine years after my RARP when a palpable nodule was detected; (2) it was ten years after my RARP when my PSA rose above detection for the first time (0.11); the nodule showed significant uptake on the PSMA PET scan; (3) three months after my PSA rose to 0.11, and just before starting RT, my PSA remained unchanged (0.11, Quest; 0.094 Labcorp ultra sensitive); and (4) three months after finishing RT my PSA is 0.086.

Summing all that up, I caught and treated my recurrence about as early as possible. In reality, if the SUV max was 3 or 8 or 10, I don’t think that would have changed the course of things one bit. I’ve said this before, but it was regular DREs that first signaled a local recurrence. A PSA of 0.11 (or 0.094) without a palpable nodule probably would have put me on surveillance rather than a course of treatment. There but for the poke of a finger…