Is a PSMA-PET scan of value if you have already started ADT treatment?

There is data showing that accuracy of pet scans diminishes with psa levels below .5 Jayhawk a poster on here had a graph once that showed accuracy vs psa level

@gkm
These are good questions for your friend to asked his urologist. His urologist seems to be cautious and trying to do what is best. We can give you our experience or suggestions but we are not medical experts. I did not have surgery just radiation but read and researched to a ridiculous amount.

If you have your prostate removed you should not have a detecatable PSA level. If you do and continues to rise it is a sign of the cancer was outside of the prostate at time of surgery. I am not sure I am passing on what you were asking. A PSMA would normally be done PRIOR to surgery or radiation to determine if there was any signs the cancer had moved outside the prostate. That should have been done prior to surgery or radiation.

You mentioned taking hormone treatments. The hormone treatments do not kill the cancer cells. They limit their ability of cancer cells to grow by hindering testostorone which fuels prostate cancer cells. A PSMA would show were the cancer cells are showing up. The question of "If you have a PSMA do you need a bone scan?" I do not know. I do know I was given both along with Decipher test.

PSA is not a perfect test. If you have a prostate many things can cause your PSA levels to go up. Trying to rule what is the cause is hard. My PSA was within normal levels but my PCP did not like the rising numbers over the years and referred me to urologist.

High PSAs and rising PSA is why MRIs and biopsies are done. An irritated prostate is going to have rising PSA levels and thus need to find out the cause (prosate irritation or cancer). When you remove the prostate and still have rising numbers it is a whole other issue. Your friends urologist suggesting PSMA is a sign you have a good one.

Here is my personal opinion:
They should have done the PSMA scan before starting the drugs to find out where the cancer was still at. I think they messed up. Now with the cancer suppressed the likelihood of finding it with a scan is low and even if found it most likely won’t show all of it. Had it been scanned with that high of a PSA it should have lit up the cancer easily and possibly a curative rather than suppressive treatment plan could have been implemented. I speak from personal experience. You never mentioned where this occurred. I think it’s time to go elsewhere for that second opinion. Somewhere that specializes.

My personal opinion is ABSOLUTELY YES. I am not a doctor and I recommend the patient ask a doctor the detailed questions to understand the relationships between these two indicators. My understanding is while PSA and PSMA-Pet scan both can indicate cancer levels they use completely different mechanisms to detect cancer and that the newer PSMA based pet scans can detect much lower levels of cancer than previous pet scans. Most importantly the pet scan will tell you where cancer exists in your entire body. PSA is only an indicator for cancer in the prostate.

In my case prostate biopsy indicated it was unlikely my cancer had spread beyond the prostate but my care team scheduled a pet scan which would have detected if any cancer was in any of my lymph nodes or elsewhere in my body. Fortunately my scan showed the cancer was only in my prostate but if it had spread elsewhere I would have wanted to know.

I visited 6 doctors including urologists, oncologists, radiation and surgery specialists before I selected my doctor and treatment. The biggest lesson I learned was that while all of them were well intentioned their recommendations for types of tests is limited by their specialized knowledge and testing resources readily available. In the end I went to Mayo Phoenix because they gave me more options than all the other doctors combined.

Many doctors are giving PSMA pet tests even though the PSA has dropped a lot. If there is a metastasis, it will show up even though the PSA is low. If it is below .2 a small metastasis may not show up in the test, but major ones will show up and that’s what you’re looking for.

They should’ve done a PSMA pet test before the RP and also before putting them on ADT. Some urologists do not understand that. That’s why you want an oncologist handling the case.

After surgery, the PSA should drop to almost undetectable. The fact that it is so high means that there must be something else producing PSA so a test now would make sense, definitely should not wait with it rising so much.

I guess my concern is that the starting of ADT probably nullifies the ability of the PSMA-PET scan to identify the location of the remaining cancer cells.

hi, gkm. No expert here, but
Because of a suspicious area ADT was advised for 3 months. After which if the node was gone, they would know that it was cancerous. If the node maintained low SUV and lit up on the PSMA PET, they would know that it wasn't cancer. The advice now after treatment that did not treat the suspicious node is to wait for several months after ceasing ADT to have another PSMA/PET.

A PSMA-PET scan is not the standard of care in Canada. I believe it was the oncologist that placed him on ADT but that raises the question why was a PSMA-Pet scan not recommended before starting ADT. Does the taking of hormone therapy negate the ability of the PET scan to detect the cancer?

As I mentioned, if you have a large metastasis, it will show up even though you have a very low PSA.

Access to PSMA-PET in Canada would vary province-by-province, I'd think. I've added the criteria for getting a PSMA-PET scan in Ontario for prostate cancer to the end of this message (you can also make a special application even if you don't meet the criteria).

Note that the chemical markers for the scan weren't approved by Health Canada until 2022 (pharma companies always apply for approval in smaller markets like Canada later), so the scan wasn't available to me in 2021 when I was diagnosed. However, I did get MRI, CT, and bone scans, all of which showed only the one big metastasis on my spine. The fact that I've had no recurrence after 3 years and my PSA remains < 0.01 gives me a fair bit of confidence that there are no other metastases at this point, but of course, there could be (and likely are) individual dormant cancer cells that even a PSMA-PET scan wouldn't pick up. If my cancer comes back, it will start with them.

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Eligibility Criteria: Prostate Specific Membrane Antigen (PSMA) PET in the following patient populations:

Initial staging of patients with a new diagnosis of high-risk prostate cancer being considered for radical (curative) therapy

OR

Staging of patients with recurrent prostate cancer who fall into one of the following pre-defined cohorts:
Post-prostatectomy node positive disease or persistently detectable PSA
Biochemical failure post-prostatectomy
Biochemical failure following radical prostatectomy followed by adjuvant or salvage radiotherapy
Rising PSA post-prostatectomy despite salvage hormone therapy
Biochemical failure following treatment for oligometastatic disease
Biochemical failure following primary radiotherapy
Rising PSA and/or progression on conventional imaging despite prior second line hormone therapy or chemotherapy for castrate resistant prostate cancer
Where confirmation of site of disease and/or disease extent may impact clinical management over and above the information provided by conventional imaging (requires a case-by-case review)
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Source: https://www.ccohealth.ca/en/what-we-do/general-health/pet-scans-ontario/oncology-indications