Steady PSA no uptake on PSMA SCAN

This happens sometimes. A few possibilities to discuss with your medical team.

First, with this recent PSMA PET scan, was there any uptake at all - including any non-cancerous areas)?

Second, PSMA PET scan results are highly dependent on the aggressiveness of the prostate cancer. The lower the PSA, the less likely a PSMA PET is to detect it (and vice versa). At a PSA of 1.12, a PSMA PET scan will positively detect active prostate cancer about 87% of the time; that also means that it will miss it about 13% of the time. (See attached chart.) You might be in that 13% group.

Third, about 15% of prostate cancers are PSMA-negative, meaning that they don’t produce any PSMA (or too little to be detected with a PSMA PET scan). PSMA PET scans out-perform the older PET scans if there is PSMA expression; however, if there is no PSMA expression, the older PET scans might perform better, the two older PET scans are:
> F18-Fluciclovine PET/CT: (trade name: Axumin®): FDA approved in May 2016.

> Choline C11 (Carbon 11) PET/CT: FDA approved in September 2012.

(Ask if you can get either of those pre-PSMA PET scans.)

Fourth, performing a PSMA PET scan too soon after the radioisotope is injected can result in a false-negative result. (How long did they wait after the injection to do the scan?) Most clinical guidelines recommend a period of about 50 to 60 minutes post-injection before imaging begins. After injection, the radioactive ligand needs time to circulate through the bloodstream, and bind to PSMA on cancer cells. If the scan starts too early, the tracer has not had enough time to accumulate sufficiently inside small tumors. As a result, the tumor-to-background contrast remains too low, meaning tiny or low-density cancer lesions may blend into the background.

Finally, consider getting a second opinion reading the scan. Just as with an MRI or a biopsy, interpreting a PSMA PET scan is a medical professional’s educated and experienced opinion of what he (she) believes he sees in the image. Much of the interpretation of scans (as well as tissue slides) is as much an art as it is a science, and depends on the skill and experience of the person interpreting them. This is why it’s so important to get a 2nd opinion (for corroboration and confirmation) of any medical interpretations.

(Which PSMA PET scan did you have: Illuccix®, PYLARIFY®, or Posluma®?)
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@brianjarvis I did have to wait an hour after my injection. Also they wanted me to be hydrated before I came in for the test.

@firespooks Hydration is very important because they want you to quickly excrete the radioactive ligand that was injected.
As a result, your kidneys, ureters and bladder will show uptake in the PSMA PET scan - even though there’s no prostate cancer there. (Did your PSMA PET scan indicate activity there?)

It means there is a recurrence somewhere that is not growing much (or at least not producing more PSA). If imaging cannot find a spot to zap the other option is systematic treatment. That starts with ADT. With stable PSA is treatment worth the negative side effects? If no treatment now should monitor every few months so you can take action if PSA starts to increase.

The fact that your PSA isn’t rising is a good thing, Regular prostate cancer is apparently not growing and spreading.

The problem is that after a long time, the prostate cancer can change and become neuroendocrine prostate cancer. That cancer doesn’t produce PSA, which could be why your PSA isn’t rising. Neuroendocrine prostate cancer does not produce PSMA so it can’t be found on the scan. You need to do an FDG PET scan to find it since it consumes glucose which regular prostate cancer does not do.

It could just be that your cancer isn’t active anymore, Or is growing so slowly that it can’t be seen in the scan.

I had a prostatectomy in 2010 and salvage radiation in 2014. After all these years, I worry about having it change to neuroendocrine.

Lots of options to talk to your doctor about.

Good to know Jeff . I’m seeing my Oncologist this week . Thanks ,

@jim18 Yes that’s exactly what I’m doing. Thanks

Not sure if the same rule applies to SRT, but you usually have to think about another recurrence when PSA rises a full 2 points above your lowest reading after treatment.
So at 1.12 more or less, I guess you are in a ‘good’ groove and monitoring with blood work is about all you can do at this point.
Phil

That’s exactly what I’m doing 😊

@firespooks, what did you learn at the appointment with the oncologist? How are you doing?