Why no PSMA expression from GA PSMA scan?? Help!

[Flydoggy]

PSA is at 2.1 for my second recurrence after initial RP and salvage radiation 4 years ago. Diagnosed Gleason was 5+4=9. Had a lymph node removed last Sept after first recurrance when GA PSMA scan showed 2mm mass. lymph node tested negative for cancer. ADT for 6 months finishing in January 2019 lowered PSA to undetectable. It began to go up again in June at .18. Question is: I just had another GA PMSA scan at UCLA and there was no PSMA expression. Anyone have any thoughts as to why that would be? Where do I go from here?

[Tall_Allen]

Because your metastases aren't big enough.

[Fairwind]

Not all PC tests positive for PSMA..Only about 80% does...

[Samdres]

Hello Tango65

I read in other post about you got LU177 prior to any treatment, wondering if that is true and would you recommend that bc you got better results ? My dad has prostate cancer metastasis to bladder ( 3 cm tumor size ) and liver (multiple). Our doctors appointments are at 26 of this month at jhon hopkings hospital in Washington DC and the next day at Georgetown hospital in DC too ( I hear that they are doing proton therapy with less side effect ).

Please let me know your thoughts, I will be greatly appreciate it. Also I'm looking for PET SCAN in USA, do you know where can i find it?

thanks a lot

[Flydoggy in reply to Samdres]

I haven't had the Lu 177 treatment.

[Hidden]

The most informative study that I have found on the subject under discussion:

"Diagnostic performance of 68Ga-PSMA-11 (HBED-CC) PET/CT in patients with recurrent prostate cancer: evaluation in 1007 patients"

link.springer.com/article/1...

It is complemented by an excel spreadsheet where one can insert personal data and get a positive detection probability estimate.

The attached excel file has been derived from 755 patient's data.

In the text, sets of coefficients are given for diffent subgroups that can be inserted into said excel for finer granularity.

For example, the (important) PSADT parameter is not addressed in the 755 patient's version because it was not known for all of them.

Tables 4 and 5 supply two sets of coefficients derived from a subgroup of 260 patients of known PSADT.