I don't know of another mainstream treatment in this case.
There's life-long hormone therapy, but that's not a curative treatment and might eventually fail if you live long enough.
Another possibility is to have a PSMA PET scan, but with a PSA of only 0.2, it might not show anything yet. They might insist you wait until it's higher before booking a PSMA PET scan, and that does risk it spreading. If it does show something, it could be away from the prostate bed, and might be amenable to stereotactic radiotherapy. However, with the R1 (was it positive margins?), it's most likely to be in the prostate bed