One problem is that you’ve waited a little too long before doing radiation. As a result, the American Society of clinical oncology (ASCO) recommends that you have ADT. You could Put it off until you come back from your trip. It may allow the cancer to grow a little bit, But it is an option. One thing is you do not have a higher risk case since you are a 3+4.

When I have my first ADT shot after my cancer came back, following a prostatectomy, I didn’t even notice the side effects And two months later, I had Eight weeks of salvage radiation. It was a six month shot. 2 1/2 years later when I had to go on ADT full-time then I noticed the side effects.

I’m 78 and I’ve been on it for eight years. I have no fatigue at all nothing that would prevent me from really getting out there and doing whatever I want. I walk a mile at high speed twice a day and I go to the gym three days a week to get weight exercises.

Check out the recommendations from ASCO

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.

This article discusses the above;
https://ascopost.com/news/march-2023/psa-level-at-time-of-salvage-radiation-therapy-after-radical-prostatectomy-and-risk-of-all-cause-mortality/