You do want to get the PSMA pet test soon, two weeks maximum. If you have to wait longer than it may not be the right time.

The double time of your PSA is very important You only told us the current PSA what was it the previous month or quarter, or the month/quarter before that, How quick is it doubling? If it’s Doubling in two months, then you need to get radiation immediately. If it’s taking 9 months, different timeline, maybe different choices.

Please look at the information below, You are at a pretty critical point so you may want to get that Radiation going ASAP.

From Ascopubs about what PSA to do salvage radiation.

≤0.2 ng/mL:
Starting at this level maximizes disease control and long-term survival. Patients treated at PSA < 0.2 ng/mL achieve higher rates of undetectable post-SRT PSA (56-70%) and improved 5-year progression-free survival (62.7-75%).
Delaying SRT beyond PSA ≥0.25 ng/mL increases mortality risk by ~50%.

0.2–0.5 ng/mL:
Still effective, particularly for patients with low-risk features (e.g., Gleason ≤7, slow PSA doubling time). The Journal of Clinical Oncology recommends SRT before PSA exceeds 0.25 ng/mL to preserve curative potential.

0.5–1.0 ng/mL:
Salvage radiation remains beneficial but may require combining with androgen deprivation therapy (ADT) for higher-risk cases.