This won't help much but, I'm interested in your research here. I think you are basically correct, it's more of a delay tactic than anything else.

From what I've found ADT seems to just starve/weaken the cancer cells so they can't multiply but doesn't actually kill them. My guess is it's believed that weakening the cells this way may make IMRT and other radiation protocols more effective.

If this is correct, then yes the time on ADT does seem arbitrary. My surgeon wants me on ADT for two years but doesn't really give a good reason as to why.

My radiation oncologist seems ambivalent on the subject and tells me ADT only accounts for a 3%-5% better outcome when taken with IMRT. I did see stats that suggest 18 mos to 2 years is 35(ish) % better than 6 mos, but if that only applies to 3%-5% of all patients anyway......?

If all this is true, taking it for two years seems to be for the purpose of letting you have that time with little or no cancer growth, if there is any cancer left. So, are we just postponing the inevitable by taking this? Creating time for better treatments to hopefully come along?

Unless somebody here or on my team convinces me otherwise. I'd rather stop at 18 mos, (seems to be a new common time frame) and see what happens. at least if I'm not resistant, I can go back on it, if the PSA starts to climb. No?

Sorry I couldn't offer more help / info, I'm just going down the same road mentally and I'm interested in others opinions on this as well.
Best of luck to you!

@haft2hunt, I'd like to add my welcome. Your question about length of time of ADT with metastatic prostate cancer is something members often ask about. For this reason, I moved your question to this existing discussion:
- Lupron Treatment Duration: How long were you on it? https://connect.mayoclinic.org/discussion/lupron-treatment-duration/

I did this so you can read through previous posts and connect easily with members like @web265 @rxharleydude @spryguy @craigc @scullrower @melcanada @yell0wsub @ken1946 and many others.

You may also be interested in these related discussions:
- Stage 4 prostate cancer treatment options: https://connect.mayoclinic.org/discussion/stage-4-treatment-options/
- Lupron yeah or Lupron nay that is the question. https://connect.mayoclinic.org/discussion/lupron-yeah-or-lupron-nay-that-is-the-question/
- Metastatic Castration Resistant Prostate Cancer https://connect.mayoclinic.org/discussion/metastatic-castration-resistant-prostate-cancer/
- ADT how long post Radical Prostatectomy & Radiation Therapy? https://connect.mayoclinic.org/discussion/post-radical-prostatectomy-and-adjuvant-radiation-therapy/
- Anyone considered bilateral orchiectomy: Why or why not? https://connect.mayoclinic.org/discussion/bilateral-orchiectomy/

It's such a confusing burden to have to weigh treatment options with so many unknowns.

I’ve been on Lupron since 2016. My cancer became Hormone Resistant last year (2021). I went to LA for PSMA PET scan which showed four pelvic lymph nodes with cancer. I underwent 5 SBRT treatments in January of this year (2022). Current PSA is <0.008. I am still getting Lupron shots, two per year, and taking Nubeqa. I will follow this regimen for 12 more months, when I will try to wean off all treatments, carefully watching the PSA for any return of my cancer. Feeling hopeful. I was first diagnosed in 2001. I’m a believer in the new more sensitive scans. Best wishes to all.

There are various schools of thought on the use and length of Lupron. I will give my clinical history (see attached). After surgery and SRT failed and with clinical data showing an aggressive PCa, I chose triplet therapy when the C11 Choline scan showed four PLNs but no bone or organ involvement. The treatment plan Dr. Kwon recommended included 24 months of ADT, six cycles of taxotere and 25 radiation treatments, 45GYa to the PLNs, all of them, with boosts and wider margins to the four identified in the scan.

Given my response to the treatment and various articles I had read about 18 vs 24 vs 36 months of Lupron, I asked if I could stop the Lupron at 18 months, Dr. Kwon agreed.

You say you did RP and 40 rounds of IMRT, was the IMRT to the prostrate bed as is generally done in SRT when you have BCR after surgery? if so and you have PCa in the PLNs then do some homework on doublet and triplet therapy.

You could do six , 12 or 18 months in combination with ADT, if your response is positive, PSA drops to undetectable and stays there, you could stop the Lupron and then actively monitor through frequent PSA tests and consultations with your medical team. If, when, you do stop, decide what the frequency of those lab tests and consults would be, maybe initially three months and adjust longer or shorter depending on the results. Have decision criteria about when you would go back on treatment, at what PSA would you image, how many test results and how far apart indicate PCA is on the move again...

As a general rule, men on ADT do at some point become castrate resistant, the questions is how long is that? If you're familiar with statistics and the Bell Curve, you'll understand some will get very short periods, other very long, most somewhere in the middle.

If you are doing ADT, consider asking your medical team about Relugolix - https://www.cancer.gov/news-events/cancer-currents-blog/2021/fda-relugolix-prostate-cancer-androgen-deprivation-therapy#:~:text=Relugolix%20is%20known%20as%20a,that%20patients%20take%20every%20day. It does not have the flare Lupron does, better CV and Metabolic side affect profile and T returns faster than when you stop Lupron. It can be more expensive depending on your insurance and requires greater self disciple since you must take it daily at home vice a 1, 3, or six month shot in your medical team's office.

You don't talk about the radiation treatment plan but if you are meeting with a radiologist, discuss the total dosage, treatment fields and boosts to the sites identified in the imaging.

If you are doing 18-24 months, you could assess whether or not the single ADT agent drops your T to <20, ideally <7, if not, you could add a 2nd ADT agent such as Zytiga, Xtandi...Lupron shuts down the T produced by the testicles by some is produced by the Adrenal glands and there are ADT drugs which shut that down.