PSA vs PSMA

[xpbdb]

I had a Ga-68 PSMA PET/MRI 18 months ago that showed 4 lesions: Two in the prostate bed, one in a seminal vesicle, and one in a pelvic lymph node (biopsy confirmed). My PSA at that time was 1.8. I went on hormone therapy in October 2018, which dropped my testosterone to around 20, and my PSA to around 0.2. That worked for about 2 months and then my PSA started rising again steadily every month through 2019. Last October I started Xtandi, which I still take. It along with the Lupron has my PSA at 0.2 or 0.3. I am wondering if I get another PSMA PET scan now will it show anything with my PSA so low? Is there a direct relationship between PSA level and PSMA expression?

[tango65]

The detection rate of Ga 68 PSMA changes with the PSA. With a PSA of 0.2 is around 40%. and around 75% with a PSA of 1.8 .

ncbi.nlm.nih.gov/pmc/articl...

Did you ever get whole pelvis radiation treatment?

[depotdoug in reply to tango65]

So theoretically my PSA 30 days in on Lupron #1 shot was 1.100ng/mL Dec 10th. Started additional Abiraterone 250mg daily 12/17 and my 2nd 90 day Lupron shot. My latest and greatest PSA 01/22/2020 was still @ 1.50ng/mL.

Do I qualify for my next 68Ga-PSMA-11 Scan in March? I'm close to the 75% detect rate.

Need to convince my MO before March 10 visit.

Qualify or no qualify?

[tango65 in reply to depotdoug]

You should get it if you and your oncologists think it will change the treatment you are getting and if you PSA does not go down significantly. Your PSA could be very low in March with the treatment of lupron and abiraterone.

Best of luck!!

[depotdoug in reply to tango65]

Thank you sir. Yes, I was hoping for a larger drop(decrease) from 1.100ng/mL 12/10 compared to 01/22/2020's constant almost 1.50ng/mL PSA.

My MO's RN told me on a call last week not to worry about PSA 1.50 while only on Abiraterone 250mg for 38 days, yet. PSA test was from a different lab in FW not Indy, plus just 38 days in on Abi.

Understand your point "if it will change the treatment I am on".

Yes, I'll get another PSA/T-level blood lab Dec 10th. Can't wait, or have to wait. PSA should be lower than pre-Abi med start. My problem is being a patient, patient waiting for my next "test lab" results document.

Thanks for cheering me on.

Depotdoug

[tango65 in reply to depotdoug]

Best of luck on this journey, your fellow traveler

TG

[xpbdb in reply to tango65]

Thanks for the resource. Never had whole pelvic radiation. Never had surgery. Started 8 years ago with IMRT, Gleason 3 + 4. Two years after that cryotherapy. Two years after that high dose brachytherapy. Two years after that hormone therapy. No more treatments available to me until beta tagged PSMA becomes available in the US. I just want to know where the devils are in my body. Since it got into my lymphatic system it could be anywhere. Fluorinated PSMA PET imaging agents will come out later this year, so I could go to any imaging center for a scan.

[Tall_Allen]

What would you do differently about it if you found something or if you didn't?

[LearnAll in reply to Tall_Allen]

... "what will you do differently " if you find some little devils hiding in your body. This is an extremely valuable question.

Knowing nitty gritty details of our cancer cells dance can be an amusing and entertaining enterprise . But if these findings do not lead to any actionable response ...they are all but futile..

[xpbdb in reply to Tall_Allen]

I would like to go after my cancer with Lu-177 or Ac-255 PSMA. It has to be PSMA avid for a chance to work. I know I am not end stage, but I am still stage 4 refractory metastatic PC. It has been 18 months since I had a PET scan. I don't want to wait until things are dire. Trying to be proactive. Lot's of new things coming soon to the US so we won't have to spend an arm and a leg to go to Europe or Australia.

[Tall_Allen in reply to xpbdb]

I don't think that "being proactive" is a good idea with respect to cancer. You can only deal with things as they are - you have no idea what direction they will go in, and you may turn them in a bad direction. For example, if you get a Lu-177-PSMA treatment while your cancer has minor PSMA expression, will that unleach your non-PSMA-avid cancer? You can't know until clinical trials are done.

[ian222]

Both identify tumor cells, but only PSA does it at the level of micro metastases. Too small lesions will not be discernible in PSMA images.