There has been much discussion on this topic. There are a number of reasons why the PSMA PET scan results were negative:
1. There were actually no PSMA-positive lesions.

2. Your PSA was so low (0.17); at that low PSA, PSMA PET scans will miss about 70% of prostate cancers even though you suspect something is wrong due to the rising PSA.

3. About 15% of prostate cancers do not express PSMA (or very little PSMA). (This is referred to as being PSMA-negative or PSMA-naive.) So PSMA PET scans won’t even see them even though you suspect something is wrong due to the rising PSA.

Has your doctor recommended using a older type of PET scan, one that isn’t dependent on PSMA - like the older Axumin or Choline C11 or FDG PET scans - which might be able to detect the location of the recurrence that is causing your PSA to rise? (Mayo Clinic often uses the older C11 Choline PET scan for this purpose.)

Dr. Kwon (of Mayo Clinic) indicates that only 1/3 of men who have recurrence following prostatectomy have recurrence only in the prostate bed, and that they should not get salvage radiation there unless they’re absolutely certain of the location of recurrence. He says to first confirm where the recurrence is. See Dr. Kwon’s presentation about recurrence (https://youtu.be/Q2joD360_pI) and what actions to take if uncertain.