Connect
Why would PSMA-PET scan fail to detect known primary GG2 tumor?
Background: I had a recent TRUS biopsy resulting in 4 out of 12 cores positive, one 7(3+4) and 3 were 6(3+3) for a GG2 Favorable Intermediate Risk. Doc ordered GPS genetic test on the biopsy tissue which scored 47 (meaning a 58% likelihood of adverse pathology which means if I had RP, the Gleason Grade would be raised >GG2. The doc said he would not recommend Active Surveillance after seeing the GPS score so I should begin learning about treatment options.
To determine extent of disease spread, last week, I had a PSM-PET scan (F-18 Pylarify isotope).
Incredibly, the results state "No focal radiotracer uptake within Prostate"! Apparently the scan failed to "light up" at the exact location where there is confirmed GG2 cancer so I ask how could it detect small, distant cancer cells or show extracapsular extension?
I immediately messaged my busy doctor to ask if I was missing something here. After a week I (nervously) await a reply.
Has anyone else run into this or can offer some explanation?
[The results did report two locations with radiotracer uptake (radioaccumulation). One was stated as "normal radiotracer accumulation of the spleen, pancreas and the adrenal glands" and the other was "mild diffuse radiotracer accumulation within ... apex of the right hemithorax... unchanged from previous CT scan in June 2016". Neither of these appear worrisome but showed that there were radioisotopes present in my system.]
Like
Helpful
HugInterested in more discussions like this? Go to the Prostate Cancer Support Group.
Connect
PSMA PET scans are not 100% accurate. Sensitivity is dependent upon many factors, including tumor size. Many studies including the following: https://www.ncbi.nlm.nih.gov/pmc/articles/PMC8832487/. Your doctor should be able to explain why this is possible. It is one of the reasons that prostate cancer often does not show up with low PSA values (< 0.4) after the removal of a prostate.
-
Like -
Helpful -
Hug
2 ReactionsSorry for taking so long to get back to you, jsh327. Thank you very much for your reply and link.
As you may have sensed, I was quite worried about my scan when I posted.
Since my posting, I have heard back from my Urologist. I also had a visit with my Radiation Oncologist, he showed me the scan images and how the bladder lights up in a way that can obscure small areas in the prostate. He also checked with their Nuclear medicine/radiology specialist. Thankfully they have assured me that there is no evidence of metastatic disease.
One thing I learned is the concept of micro and macro sites and, if I understood correctly, the cells which can be seen under the pathologist's microscope may not be sufficient to light up on a PSMA-PET scan. So, one concern I had was that I might have one of the more aggressive cancers that don't show up in PSA or PSMA. But the doctors explained that the biopsy tissue would show that "highly differentiated" tissue.
Thanks again!
-
Like -
Helpful -
Hug
6 Reactionsmulberry, your post is so interesting. Thanks
As I understand it, the PSMA PET detects cancer cells that express PSMA on their surface. If cancer cells have a low volume or express little to no PSMA, this particular scan may not see them.
Have you ever had a 2nd or 3rd Opinion of your Gleason Score ( Pathologists ) Biopsy Results ?
No, I only had the initial biopsy pathology but my post-surgery pathology results confirmed the 7 (3+4) GG2 classification of the biopsy. My PSA was 0.009 at 3 months and 0.006 at six months so, happily, no additional treatment was needed.
-
Like -
Helpful -
Hug
1 Reaction