The question you ask is what many face after surgery and a rise in PSA at some point after that.

Clinical data may inform your discussion with your medical team. Some of that data may be in your pathology report from surgery:

Gleason Score
Grade Group.

Other clinical data may be from labs - PSA Doubling and PSAV

MSKCC has some nomograms which may be useful in any decision making - https://www.mskcc.org/nomograms/prostate

I had BCR 18 months after a "successful" surgery. My clinical data is indicative of high risk which factors into my decision making - GS 8, GG4, 18 months to BCR, rapid PSADT and PSAV.

I have seen general rules of thumb with regards to PSADT:
< 3 months - treat
between 3-12 months - use in conjunction with clinical data to decide treatment
>12 months - consider continuing to actively monitor

Another factor in play is imaging, the likelihood that a PSMA PET shows where recurrence is. Intuitively, the higher one's PSMA, the greater the likelihood a PSMA scan shows the recurrence.

I guess the question is, what are your clinical risk factors and how aggressive do you want to be?

You have choices:

Continue to monitor with labs and consults, image at some point, then discuss with your medical team. When you and with what agent you would image is a discussion with your medical team. A consideration is any risk in waiting for an increase in your PSA to image. That questions may be a function of your clinical data and risk stratification, high, intermediate, low...

Act now,,,,

If you decide to make a treatment decision now or later, you have even more choices,

You could do radiation to the prostate bed, SRT
You could do SRT and also the whole pelvic lymph nodes (WPLN)
You could do SRT, WPLN and add ADT for a definitive time, 6-12 months.

Imaging may better inform these decisions.

If the latter, you may face two other decisions on ADT, which agent, whether to add an ARI,

As to the side effects of radiation, today's radiation is not our father's. I had SRT, WPLN and SBRT, 69 treatments, 160 Gya total, zero SEs, testimony to the advances in planning and delivery as well as the skill of my radiologist and her team.

The SEs of ADT are well known but can be mitigated:
Exercise
Diet
Managing Stress.

For short term, especially when using Orgovyx, recovery of T can be fairly rapid, starting at 3 months.

I am not 17 years after my surgery, experiencing what you are, but, were I you I would:

Do nothing right now.
Continue with labs and consults every three months.
Discuss with my medical team about decision criteria on when to image.

If, when I reach that point, image, then decide informed by all the clinical data possible,

There is some evidence that MDT in the case of oligometastatic PCa can push the need for ADT down the road.
There is also the likelihood that when imaging shows where recurrence is, there is micro-metastatic PCa too small to be seen so systemic therapy is added to MDT.

ADT + ARI may be overkill if the PSA drops to undetectable in the first three months of SRT+ADT or SRT+WPLN+ADT.

Kevin