Minimum PSA for GA-68 PSMA Scan

[dmt1121]

My PSA rose, but only a very minimal amount. I have been on Eligard and abiraterone for five years and my PSA has always been <.05 ng/ml and my last test came back .05 ng/ml with all PSA tests performed at the same lab.

My new oncologist wants me to have a GA-68 PSMA scan which seems premature on two levels. First, my PSA seems very low to detect PSA for this scan. Second, I only have one increase in PSA and always thought there needed to be at least three tests to show a trend and to reach the threshold for the scan.

My question is what is the minimum threshold for my PSA level for the GA-68 PSMA scan to be effective? Please cite your sources, so I can refer to them with my oncologist.

Thank you.

[StayingOptimistic]

mine was also <.05 for about 16 months since I stopped ADT. When it rose to .2, MO ordered the psma scan. The day I got the scan, it was already .32. It found LN Mets in abdomen and pelvic. I then went back on ADT.

[dmt1121 in reply to StayingOptimistic]

Thank you.

[Tall_Allen]

Look at the table (links in table) at the end of this. If you think you want at least a 50/50 chance of showing metastases, you would wait until PSA reaches 0.5 ng/ml:

prostatecancer.news/2016/12...

BTW - 18F-rhPSMA-7 was just FDA-approved last week. It will probably be a few months until it is widely available.

[Magnus1964]

Eligard and abiraterone for 5 years , Congratulations. Stick with it and milk it for all its worth. Your doing great. Don't let some doctor talk you into something else.

[allmo]

I was in the trial at UCLA that resulted in Gallium PSMA and in the trial at Stanford that resulted in Pylarify both getting FDA approval. One of only 27 patients that got both studies at the same time.

The qualifying PSA level for both trials was 0.2 ng/ml. Pylarify minimally outperformed Gallium reporting a detection rate of 40-50% at that low number. In fact, Pylarify picked up 3 bone mets in me at 0.2. Perhaps had I waited till 0.5, I would not have qualified for the definition of "oligometastatic state" and thus metastasis-directed therapy.

"The clinical utility of piflufolastat F18 PET/CT is supported by this analysis in men with low PSA levels that range from 0.2ng/mL-0.5ng/mL."

urologytimes.com/view/analy...

[Bethpage in reply to allmo]

This is interesting. Thank you for the background! My husband was the last patient in Stanford's trial. F18 barely found his recurrence at PSA 1.0. All other sensitive scans (including C11-choline, failed but he did not have the Gallium PSMA.

[TJGuy in reply to allmo]

I also was in the UCLA trial, and also did a trial at MAYO comparing MAYO Choline vs Gallium PSMA.Several things to remember and it's a combination of these, the more aggressive your cancer is the earlier/lower PSA you can see it.

If your cancer is in one spot you will see it earlier than if your PSA is split up over multiple instances.

Some PC cancers in the range of 6-10 % of PC doesn't espresso PSMA.

I've have times when scans were not definitive at 1.5 or below but we're when I reached PSA of 3.9 showing 5 instances of PC. Pelvic bed and Whole pelvic radiation at that point

I've have another time when two adjacent lymph nodes show bright at 1.18. radiation to follow in near future.

Surgery can also be used to remove lymph nodes appearing positive on scans.

One other thing for Americans. Your insurance intervines between you and your doctor. My BCBS has denied or required other tests such as bone scan and CT scan, before they would approve a Choline or PSMA scan. They can also put peer to peer requirements to talk with your doctor before approval. You can appeal but it takes energy and lots of time.

BCBS often cites a PSA of >=1.0 before they will approve. If you're on Medicare you might not be subject to all this.

[bldn10]

Are you graduating from a urologist to oncologist or just switching oncologists? Does this oncologist specialize or even have a particular interest in advanced PCa? If not, see if you can find one who lives and breathes PCa, reads all the literature, stays up on new developments, etc. In the 22 years since my Dx I can't count how many wasted tests, scans, etc. I've had.

That said, I'm recurring 6 years after SRT and will be getting a PSMA soon. Oliver Sartor, a med-onc of renown, told me .3 and my rad-onc, who will be doing it, said .5. The higher PSA is the more accurate the scan is, but how high do you really want to let it go?

[dmt1121 in reply to bldn10]

That is an interesting issue for me. I have had three oncologists prior to this one. The first change was because I moved. The second was because I was unhappy with my oncologist (she was burned out from the pandemic and being a single mom). Last but not least was my last oncologist (who I liked), who left to take a position as a senior cancer researcher with Genentech.

My new oncologist had a primary focus on PCa during his fellowship but ended up focused on lung cancer. That being said, he has several PCa patients and is in touch with PCa oncologists when needed. Prior to going to my new oncologist, I had decided to go to a PCa expert. Problem was that she was spread so thin with clinical trials, teaching and seeing patients that I would likely only see her PA until my situation moves into the clinical trial realm. Based on this, my last oncologist recommended against her and instead recommended who I am now seeing.

So, here I am and assessing my new oncologist as he makes recommendations. I know he's sharp and seems on top of treatments and clinical trials but not sure he has enough experience to make measured decisions. Time will tell.

Your last question is always a personal decision based on how much risk you want to take in disease progression versus accuracy of the scan.

Maybe the magic 8 ball is the way to go! Lol.

[dhccpa in reply to dmt1121]

Encouraging and scary at same time! Trust your doctor. But which one? Sounds like you're pretty seasoned at this point.

[shortPSADT]

Just had a F-18 PSMA whole body Pet scan two days ago. My PSA on the same day as the scan was 0.484. -- no mets were found! Now I'm advised to wait until the PSA is around 1 and then have another scan. I'm sure there is cancer somewhere as my doubling time is 2.4 months.

[dmt1121 in reply to shortPSADT]

Yes, it is very individual as to when to get a scan. I had the F18 scan back in 2018 at .2 ng/ml and it showed a bone lesion in my femur and a tumor near my bladder. I went off of Lupron to allow my PSA to rise enough to have that test. It was definitely worth it but it might have ended up showing nothing.

Knowing your body, trusting your oncologist and being well informed are my ingredients for making such decisions. Right now, I am seeking what people's understanding is of a minimum PSA level for GA-68 PSMA to gain more information than the confusing information online.

Thank you for your story and good luck with your next scan.

[fast_eddie]

I was able to get an axumin scan after three consecutive quarterly rises in PSA. It was 1.8 at the time of the scan. My urologist explained that qualifying condition to me. I was not on ADT. I've not been on ADT since my HIFU surgery. The scan came back negative.