Your oncologist is correct - since you have had consecutive increases in PSA and are now approaching 0.2 - which is the definition of biochemical recurrence after prostatectomy, there really is no benefit or reason to postpone treatment - it just allows the remaining cancer cells to continue to grow, multiply and get stronger. If there is no definitive cancer identified through the PSMA PET CT, The radiation will be a wide field EBRT (external beam radiation therapy) to the pelvic area - with particular focus on the prostate bed and surrounding area (to treat any potential localized metastasis to the lymph system). They may also recommend androgen deprivation therapy (ADT) in conjunction with the radiation - the hormone deprivation in combination with radiation has been proven to offer improved curative results vs radiation or ADT done alone. Wishing you the very best outcome and lasting remission in the future.