There's a chart that shows the probabilities that mets will be detected at different levels of PSA. The studies that compare the mets found by two different scans are particularly helpful./pcnrv.blogspot.com/2016/12/pet-scans-for-prostate-cancer.html
The DCFPyL PET scan is the best so far, followed by the Ga-68-PSMA-PET.
You are correct that the probability of detecting mets is very low when your PSA is only 0.1. It is impossible to say whether that is because (1) there are distant mets that are too small to be detected, or (2) there are no distant mets yet. Therefore, even if it is negative, that does not insure that SRT will be effective - it works about
half the time.
I think you should be talking to an RO about
all this. MOs have no particular knowledge about