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How to check PSMA in our body?

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Posted 6/19/2021 8:40 PM (GMT 0)
Hi guys. I am doing some research on new PSMA scan techs. It is said that PSMA is found in more than 80% of men with prostate cancer. So in other word, you should verify you are in this 80% first, then GA68 or Pylarify will be suitable for you. Otherwise it will be useless. Just like PSA is useless as biomarker for the PSA insensitive patients. Right? So my question is: how to check PSAM in our body to make sure this new detecting machine will work for us?
Posted 6/19/2021 9:08 PM (GMT 0)
They will make sure you are a PSMA producer before you get the scan. Those that have had the scan can speak to this.

Djin
Posted 6/19/2021 9:37 PM (GMT 0)
Thanks. But how? There is also a kind of blood test like PSA? May I ask my doc to have such a PSMA test?
Posted 6/19/2021 10:11 PM (GMT 0)
The test may be on one's biopsy slides -- but I'm not sure. For those who produce it, it's found to varying degree in most body tissues in addition to the prostate. The lacrimal glands especially. My uro mentioned that men getting Lutetium-177 treatment for their PCa sometimes have eye problems for that reason.

Djin
Posted 6/20/2021 10:54 AM (GMT 0)
Hi Djin. Excellent answer. Another question: PSA and PSMA are associated with each other or not? PSA is high, PSMA could be low? PSA is low, PSMA could be positive? Or they could be totally independent? Thanks.
Posted 6/20/2021 3:08 PM (GMT 0)
The "M" in PSMA signifies it's found on cell membranes, primarily of prostate cells (for the majority of men who produce it).

Using PSMA (prostate-specific membrane antigen) evaluation on prostate biopsies for risk stratification at time of initial diagnosis. (2019)

"Conclusions: PSMA qualifies as an independent prognostic biomarker on Bx at time of initial diagnosis in addition to the established markers PSA and grade group. PSMA predicts disease recurrence following curative surgery and potentially improves the discrimination indolent vs. aggressive disease. We propose the routine assessment of PSMA expression on Bx for outcome prediction and risk stratification at time of initial diagnosis prior to treatment decision."

[Emphasis mine]

Djin
Posted 6/20/2021 6:00 PM (GMT 0)
This is from a 2004 review
https://www.ncbi.nlm.nih.gov/pmc/articles/pmc1472940/

Researchers have attempted to use PSMA as a serum-based marker, but results have been variable at best.
As a result, PSMA is not used as a serum-based diagnostic or screening marker.

More in general (copied from Dr Google):
PSA values are useful in the clinical diagnosis and staging of prostate cancer patients, and generally fall to low values in response to effective treatment, e.g., surgery, hormones, radiation, chemotherapy. PSMA values are not related to clinical stage but if elevated can fall in response to effective treatments.
Posted 6/20/2021 6:19 PM (GMT 0)
Thanks, Sr Sailor. A question: since PSMA can be produced by a variety of other organs, how can we use it for PSMA scan target? Furthermore, 177Lu treatment and other promising treatment use it as the cancer tracer? I just wonder. As Djinn said, even tears from eyes could secret PSMA. Is it dangerous?
Posted 6/20/2021 7:22 PM (GMT 0)

116grove said...
Thanks, Sr Sailor. A question: since PSMA can be produced by a variety of other organs, how can we use it for PSMA scan target? Furthermore, 177Lu treatment and other promising treatment use it as the cancer tracer? I just wonder. As Djinn said, even tears from eyes could secret PSMA. Is it dangerous?

Regarding scan reading, it's a question of training and interpretation. The amount of "background" illumination from the pickup by healthy tissue has to be calibrated so hotspots stand out. (This is true for Axumin scans also. If you look at the their website for the product "label," you'll see a table of the amount of tracer pickup by the different body organs.) Radionuclides used as tracers have a short half life (I think it's 110 min for the newly approved Pylarify) and they are essentially gone from the body in a few days. Just like men with some types of brachy implants, I imagine those getting 177 Lu PSMA treatment are given instructions about what not to do following therapy.

Djin

Post Edited (DjinTonic) : 6/20/2021 1:52:21 PM (GMT-6)

Posted 6/21/2021 1:38 AM (GMT 0)

116grove said...
Thanks, Sr Sailor. A question: since PSMA can be produced by a variety of other organs, how can we use it for PSMA scan target? Furthermore, 177Lu treatment and other promising treatment use it as the cancer tracer? I just wonder. As Djinn said, even tears from eyes could secret PSMA. Is it dangerous?

With PSMA PET scans, the radiation load to unwanted targets such as the salivary glands is relatively low, but they will 'light up'. The person interpreting the image will know this and report it accordingly.
With respect to side effects, the actual dose received by targets will depend on the radioactive tracer used (there are at least two kinds). But with PSMA therapies to eradicate cancer, the dose to unwanted targets will be much higher. However, there is no reason to believe that you would need such therapy right now.

Post Edited (Sr Sailor) : 6/20/2021 7:41:48 PM (GMT-6)

Posted 6/21/2021 6:18 PM (GMT 0)
I was in an early PSMA trial years ago and they did not do any type of testing to see if I was part of the 80%. I don’t think that exists.

I asked my doctor about the other areas like saliva glands and he mentioned that they might ice that area so radiation would not get to those areas..l have seen that with chemo for patients that attempt to keep their hair...there is a cold cap that you can wear that is to help with that...
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