What you are referring to is what is called adjunct radiation. The doctor listed below is one of the very highly respected doctors in the country. She speaks at a lot of conferences and really is extremely popular with her patients. There are 4 requirements she has for doing this radiation. You have to have two of them in order to consider it? You are pT3b So you definitely fit one of the requirements do you fit another one? That is the deciding factor. that you get at least two of them.

Adjunct radiation
Dr. Efstathiou concluded as follows:
* Early salvage radiotherapy is favored over adjuvant radiotherapy in most patients
* Consider adjuvant radiotherapy in otherwise fit, motivated, very high-risk patients with ≥2 of the following risk factors:
* pT3b-4
* Gleason score 8-10
* pN+ Lymph node Metz
* Decipher score >0.6
* In high-risk patients, use lower thresholds to initiate ‘ultra-early salvage or adjuvant-plus’ radiotherapy
* If giving adjuvant radiotherapy, it implies high-risk disease. Thus, Dr. Efstathiou would recommend treating the prostate bed and pelvic lymph nodes, in addition to short-term versus long-term ADT, depending on risk factors
* May consider genomic classifiers or artificial intelligence tools to help with informed decision-making
* The goal is to avoid (or delay) radiotherapy in those who we can, without missing a window to cure patients who are guaranteed to recur

Here is a link to the article supplied by @surftohealth88 originally
https://www.urotoday.com/conference-highlights/apccc-2024/151546-apccc-2024-debate-how-to-best-manage-a-fit-patient-with-high-risk-localised-and-locally-advanced-prostate-cancer-how-to-select-patients-for-adjuvant-therapy-after-radical-prostatectomy-and-how-to-treat-them.html
Someone posted an almost identical request in this forum a few months ago, and didn’t really get any feedback from people that had similar issues.

Many people who have salvage radiation have their cancer come back, but that is quite similar to adjunct radiation which is what you are facing. The side effects vary, but here’s a list of the main ones.

Adjunct and salvage radiation can cause the following
Radiation proctitis
Rectal issues
Rectal bleeding
Bladder infection
Breaks in bones radiation damage to bones
Fibroses in bladder which reduces capacity

In general, toxicities after postprostatectomy radiation using photon-based techniques have been tolerable, although the rates of late grade 2 and gastrointestinal (GI) and genitourinary (GU) toxicities range from 10% to 20% with image-guided intensity-modulated radiation therapy (IMRT).

What this means. “ late grade 2 and gastrointestinal (GI) and genitourinary (GU) toxicities”
Above describes moderate symptoms of damage to the bowel and bladder, requiring minimal intervention but impacting daily activities, and occurring after salvage radiotherapy for a recurrence or persistent cancer after initial treatment. Gastrointestinal (GI) symptoms can include moderate diarrhea or bleeding, while genitourinary (GU) symptoms might involve increased urinary frequency, pain, or intermittent bleeding.

A link to article
https://pmc.ncbi.nlm.nih.gov/articles/PMC8019576/