I can't see from your Profile or this thread what your original treatment was but assume it was a Prostatectomy. If this was the case and it was not augmented by RT, it may be possible to treat your Prostate Bed and a very few lymph nodes with RT. If this is not possible or too big an ask for RT, it's likely you will be offered systemic treatment as Lyn as suggested. RT may also be given with systemic treatment. Cancer cells can sometimes advance even with a low PSA. The PSA figure you gave is quite low to be picked up even with a PSMA scan. Sometimes cancer can pause or accelerate in a way that can even surprise consultants who have detailed histology including scans to consider because men can respond differently to treatment, so we are not able to say what your individual response will be. Even the side effects of treatment can be more severe for some men than others.
Do let us know what is decided and your response to further treatment.