Will Lupron and Casodex affect a PSMA PET Scan?

[Smallfall]

In 2017, with a PSA of 9 and Gleason of 3+4 on left of prostate, I had HIFU on left side. After 6 months my PSA of 2 became almost 4. In june, with a PSA of 7 I had a biopsy. Out of 12 cores, 8 were 3+4, 1 was 4+3, and one was 4+4, that one was on the right side. I had a CT of abdomen and pelvis last month that showed no cancer outside of prostate, a MRI of prostate last year showed no cancer outside of prostate. The RO wanted to do 70 radiations of prostate and surrounding tissues. He doesn't do HDR Brachy, but I requested and he sent a refrerral to Dr. Joe Hsu at UCSF; I have a telehealth mtg with Dr. Hsu on 9/8. But the RO stil wants to do 30+ radiations on surrounding tissue after the brachy. I'm 3 hours away from the RO so I will have to rent a place for the treatments. I am going to request a PSMA PET Scan from Dr Hsu, to rule out the need for further radiation after brachy. My urologist wants to start me on bicalutamide and Lupron ASAP. My question is, will these drugs affect a PET scan?

[Tall_Allen]

"I am going to request a PSMA PET Scan from Dr Hsu, to rule out the need for further radiation after brachy. "

I think a PSMA PET scan is a good idea, but not for the reason you think. It is to rule out distant metastases. If there are distant metastases, you may decide not to have prostate radiation at all or to have a more limited treatment. If there are no distant metastases, it will be especially important to have the extra external beam treatments to the whole pelvis. Even the best PET scan can only detect tumors larger than 10 million cells.

" My question is, will these drugs affect a PET scan?"

Yes, but probably not in the way you are thinking. ADT will increase PSMA expression for a few months at the beginning. After that, PSMA detection will be reduced.

[Smallfall in reply to Tall_Allen]

Thanks for the helpful reply TA; I wish I had been in contact with this group in 2017, before I wasted time and money on HIFU.

[Teddski in reply to Tall_Allen]

Started on Lupron in November of 2018 and had the CT scan in March, so I do not believe it will cause any problem. My PSA was 14.5, did 18 months of Lupron and 45 radiation treatment. My PSA has been zero for the past nine months.

[Smallfall in reply to Teddski]

Thanks, congratulations!!

[timotur]

The answer to your question is yes, Casodex and Lupron would affect a PSMA scan by lowering the uptake of PSMA marker used in the scan and lowering the sensitivity. It appears your PCa is still contained to the prostrate, so you should get the scan to eliminate EPE, SV, or LN involvement. Distant mets usually follow those local events. Right now it appears yours is still local.

I was Stg t3b +SV as determined by an ultrasound biopsy, and used a PSMA-scan to determine I was +LN before starting Lupron. And the met at the LN was right at the SUV minimum, so if I'd been on Lupron already, it may not have been detected.

[Smallfall in reply to timotur]

Timotur, thanks for sharing your info; it prompts more questions for the urologist.