Hi Jon
I started ADT back in March with 2 weeks of tablets them my first injection. I was convinced to start the treatment even though I still hadn't decided whether to go for the op or RT by the oncologist he said it would be for 18 months to 2 years but I forgot to ask the question you're asking.
I then went for RT (mainly because the consultant surgeon said he would recommend I had RT after the op & also as I was now on ADT that part of my concerns about RT was decided) I had 2 telephone appointments with the clinical oncologist and although I'd made a note to ask her about when 18 months /2 years started I again forgot 😯. However when I got the not of our second telephone appointment itsaid " Treatment: On 2 years' neo adjuvant & adjuvant androgen deprivation therapy (which I take to be ADT) until August 2024 which is 2 years after I finished my RT! I have to say I was hoping all being well with PSA teats it would end September 23 which she had said was when she will sign me off if my PSA remains undetectable.
I am due to meet her next September (2024) and have asked to have a face to face meeting which she's agreed.
I know from a couple of friends who had ADT & RT that at the time they were signed off by oncology you have a choice to stop ADT.
I realise I've not answered your question but it seems to me they, oncologists, prefer a belt and bracers approach. As as the oncologist said "we won't fully know for certain if the RT has worked until you come off the ADT".
Les