PSMA PET CT versus PSMA PET MRI - Advanced Prostate...

Advanced Prostate Cancer

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PGDuan profile image
19 Replies

Hi, when checking for the source of BCR and low-level PSA after surgery and radiation would it be best to go with the PSMA PET CT or the PSMA PET MRI? Seems that both are available but the wait list for the CT is longer.

My PSA is still low, but up to 0.29 from 0.15 last month and <0.05 in June. If I understand recent reports the test positively identifies source 50% of the time when PSA is > 0.2.

Previous post-surgery issues were in pelvic lymph nodes that were treated by radiation. Thanks

19 Replies
Tall_Allen profile image

If it is the Siemens PET/MRI, definitely go for it! I'm very surprised that you're saying that the wait for the PET/CT is longer. There are only about a dozen PET/MRIs operating in the entire US. PET/CTs are available everywhere.

PGDuan profile image
PGDuan in reply to Tall_Allen

Hi TA, Yes I think it is the UCSF Siemens one using 68Ga-PSMA-11 . The PET/MRI includes an MRI of the pelvis which can help with local recurrence (but one can do that separately if needed). The PET/MRI will be more expensive and they indicate a three month back-log for PET/CTs, and about a month back-log for PET/MRIs.

Mind if I ask another question? Since I've already had RALP and radiation to the prostate bed is it reasonable to hope that the scan might identify avid nodes in the general prostate area but perhaps outside the template that was treated by radiation? My reasoning is thus local treatment / additional focused RT could be possible and effective. (I completed a course of adjuvant/salvage radiation therapy directed at the pelvic lymph nodes in February 2019).

Grateful for all your input.

Tall_Allen profile image
Tall_Allen in reply to PGDuan

Ah. That's because UCSF is only one of 2 places (UCLA is the other) where one can get the FDA-approved Ga68-PSMA-PET scans.

No, it is not reasonable to to hope that the PSMA PET will detect anything - a complete waste of money IMO. If you've already had radiation to the entire pelvic lymph node area in 2019, I don't see what you have to gain by more radiation to that area.

PGDuan profile image
PGDuan in reply to Tall_Allen

Ok, thanks for the perspective but I’m a bit confused. I was listening to Dr Eugene Kwan’s recent PCRI talk and took away the point that getting a PET scans when over 0.2 can really help in terms of staging (local, focal, regional, diffused) and pattern.

I’ll do more research and think through the possible outcomes and discuss with my team -- what the plan will be if a) we see something, or b) nothing is detected.

Thanks for the critical input. Getting the “you have a problem” diagnosis 3 times now has been difficult.

Tall_Allen profile image
Tall_Allen in reply to PGDuan

I (and many others) think Kwan is off-base in his assessment. He oversold C-11 Choline for many years and continues to oversell.

Bubasurf6 profile image
Bubasurf6 in reply to Tall_Allen

Hi TA I’m scheduled on October 18 Th at UCSF for a “ PSMA PETMR PANEL “Do you know if that short for PET MRI ? I’m contacting my MO to clarify also My PSA is .525 currently at my current doubling rate my PSA will be between .7 and .8 when I have the scan which I understand this is a good number to have the scan. I had RALPin 2014 followed up post surgery with Lupron and Radiation to prostate bed. Was non detectable for 1 year slow rise till 10/2018 entered 1 year UCSF trial 11/2018 PSA .820 went nondectable till 11/2020 Exactly 1 year after trial Mo believes high probability back to ADT at a minimum pending scan results. I really appreciate your thoughtful and through comments.

drmoose profile image
drmoose in reply to Tall_Allen

TA - you mentioned there are about a dozen PET/MRI's in the U.S. Is there a reference or web site which let's us find these (easily)? thanks for any tips ...

Tall_Allen profile image
Tall_Allen in reply to drmoose

You can call Seimen's who manufactures them.

Justfor_ profile image

PET/MRI no doubt.

tango65 profile image

MRI has a better definition of the anatomy, but the detection of the gamma rays emitted by the Ga 68 will depend of the resolution of the PET scan and the software the PET scan is using. It it highly technical , and beyond my pay grade, but my understanding is that the MRI is not going to get more "PSMA avid lesions" than a CT scan . It may get better definition of the anatomy and may be find lesions which were not detected by the PET scan, particularly in the bone marrow,

TeleGuy profile image

If I am understanding you right, the MRI option would just cover your pelvis but the CT option (that you have to wait for) would probably cover chest, abdomen, and pelvis? It seems to me that if you are wondering where the recurrence is you would want to have a broader look than just your pelvis.

brianlynch profile image
brianlynch in reply to TeleGuy

Actually Whole Body MRI is very effective across all major organs and body parts and does much better in soft organs than PSMA PET

j-o-h-n profile image
j-o-h-n in reply to brianlynch

Hello brian, I hate to be a PITA but if possible:

Please tell us your bio. Age? Location? When diagnosed? Treatment(s)? Treatment center(s)? Scores Psa/Gleason? Medications? Doctor's name(s)?

All info is voluntary, but it helps us help you and helps us too. When you respond, copy and paste it in your home page for your use and for other members’ reference.


Good Luck, Good Health and Good Humor.

j-o-h-n Tuesday 09/14/2021 5:47 PM DST

TeleGuy profile image
TeleGuy in reply to brianlynch

Agree, but in PGDuan's followup comment he mentioned only MRI of the pelvis.

Cooolone profile image

All good information above... If your PSA is rising, you're reaching for straws and should be considering a systemic therapy at this point rather than a whack-a-mole approach.

Also, PSA needs to be at least .5ng for effectiveness that makes it worth anything if anything, and .8ng to be best for sure.

Good Luck & Best Regards

PGDuan profile image
PGDuan in reply to Cooolone

Thanks. So it seems the consensus is to wait a little to see the PSA closer to 0.5ng.

Cooolone profile image
Cooolone in reply to PGDuan

I would say even .8ng where the PSMA scan exceeds others. But at the very least, .5ng as a threshold.

Justfor_ profile image
Justfor_ in reply to PGDuan

Consensus of silly-lazy docs that live in their binary bubble, as the real but analog (proportional) world is too much for their gray cells. Magic numbers like 0.2, 0.5, 1, 2 etc are easy to remember and to pass over to ignorant patients. Just a simple question to ask those proffessing these nonsense: What is the published detection rate for the PSA range of 0.2 to 0.5 and the same for 0.5 to 1.0.

MateoBeach profile image

The PSMA avid PLNs treated in 2019 can take years to resolve and disappear even if they have been thoroughly adequately treated with RT. It may be useful to follow their resolution but would not call for re-treatment (SBRT) unless one actually progressed. Your next PSMA scan should be wide field, from neck to thighs, to look for any avid mets outside the previously treated pelvic fields. I’m in the same situation since 2019. It takes patience.Not sure if MRI head better actual sensitivity for the PET induced gamma signals than CT or just the better tissue imaging?

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