What’s the best PSMA scan.

[Echotango51]

I contacted a imaging center today and asked about there PSMA scan. They offer the F18 PSMA, is the Pylarify better, or does it really make any diffidence.

ET

[Tall_Allen]

Pylarify (F18 PSMA) is better at detection at low PSA. It doesn't matter at high PSA.

[Echotango51 in reply to Tall_Allen]

Thank you TA

[tango65]

Between a PSA of 0.5 to 3.5 the detection rate of the Pylarify PET/CT is higher than the detection rate of the Ga 68 PSMA PET/CT. Both are well tolerated without major side effects.

[Justfor_]

In Europe the 18F PSMA 1007 has an established base. It has the advantages of 18F, like the Pylarify, plus reduced masking of the urinary track as it is excreted via the liver and not the kidneys leading to a better visibility around the bladder.

[GP24 in reply to Justfor_]

But PSMA 1007 results in more false positive lesions. Therefore it is not used that often.

[Justfor_ in reply to GP24]

I have read a couple of papers comparing 68Ga with 1007 and a third one used in Germany without a mention of higher false positives. Do you have any literature on this?

[GP24 in reply to Justfor_]

In this video from the APCCC 2022 the experts discuss different tracers and mention this.

youtube.com/watch?v=t5DBN63...(Not working as expected?)

[Justfor_ in reply to GP24]

Thanks, I will watch it.

[Justfor_ in reply to Justfor_]

The argument of the Australian guy, to say the least, is not convincing at all. His reasoning is that the 18F-PSMA-1007 scan of a patient showed 5 metastases and when they repeated the scan (to enter a RCT) with 68Ga-PSMA-11 there were none. Elementary knowledge of measurements theory states that an instrument/measurement methodology is validated only by an instrument/methodology of an accuracy at least one order of magnitude higher.

There is a number of papers claiming that the sensitivity of the 18F labeled radio tracers (Pylarify included) are more sensitive at low PSA values. This has nothing to do with PSMA but with the isotopes of Fluorine and Galium. On top of that, it is also widely accepted that 1007 is more suited for initial staging and recurrence detection after initial therapy, as it masks less the urinary track. There are two posible explanations that either, or both, can explain the discrepancy of the two aforementioned PSMA scans.

1) Some or all of the detected foci by PSMA-1007 originate from benign lesions, i.e. they are true false positives.

2) Some or all of the detected foci were missed by PSMA-11 either due to its lower sensitivity or masking.

I did some further research on the subject to learn that PSMA-1007 is considered more prone to detecting bone lesions (true or false - no one knows as they have not been biopsied). It is speculated that such metastases post RP and suspected BCR are very uncommon, hence, they ought to be false positives.

Amongst the papers that I reviewed the following from South Africa seemed to me most relevant:

"A comparison of the diagnostic performance of F-PSMA-1007 and GA-PSMA-11 in the same patients presenting with early biochemical recurrence" (2021)

nuclmed.gr/wp-content/uploa...

the conclusion of which reads:

"Conclusion: In our pilot study F-PSMA-1007 was able to detect more sites of recurrence as compared to Ga-PSMA-11 which were mainly within the prostate and surrounding pelvic structures."

As a final personal note I would like to remind the reader that all these radio tracers carry intellectual properties (read royalties), that may play some role...

[j-o-h-n]

The best PSMA scan is the one that shows no signs of Pca............

Good Luck, Good Health and Good Humor.

j-o-h-n Friday 05/13/2022 1:21 PM DST

[TJGuy]

Zirconium 89 appears far superior to lu-177. It's being developed in Germany, but articles from NIH and others, check it out. Google it.