Hi,
From what I've seen an increase of 2 above the nadir or 3 increases in psa should be investigated. Did you have a psma scan or an mri last year. A psma scan can see smaller lesions and that should be preferred. Some places don't like spending the money as they haven't got a psma scanner.
I've no experience of RT but if it was me I'd be looking for another opinion. Perhaps a PCUK nurse by phone or ask to meet an Oncologist at the hospital. Perhaps a private second opinion.
I was told I could have a psma scan at 0.5 on the NHS if it reaches that, after surgery. Also I could pay for one earlier.
There are more treatments available,, such a focal, and I wouldn't want to miss out because it got too high. If it rose by a third in 6 months it could become 4 by July and 5,2 by next Jan although you can't forecast accurately.
I wouldn't normally reply to an RT type query but I noted you said no-one replied to your last post. I had my treatment, surgery, around the same time as you and have been on here 7yrs so picked up some stuff and perhaps someone else will answer. All the best Peter