BY ANKIT AGARWAL, M.D.

 

When a man is diagnosed with high-risk prostate cancer and chooses radiation, one of the first things he is told is that he will also need hormone therapy—specifically Androgen Deprivation Therapy (ADT)— and often for a long time. Eighteen months. Two years. Sometimes three. For a lot of men this is the part of treatment they dread most, because the radiation itself is usually well tolerated, while the hormone therapy is what changes how they feel day to day.

So it is a fair question, and one I get often: if I am getting a high-quality seed implant combined with external beam radiation, do I really need two or three years of hormone therapy? Or is a much shorter course just as good?

The honest answer is that the guidelines and the best modern data do not fully agree, and the gap between them matters for your quality of life. In this article I want to walk through where the long-duration recommendation came from, what the strongest evidence actually shows, and why the kind of radiation you receive, specifically whether you get a brachytherapy boost, should change the conversation about how long you stay on hormones.

What Is ADT, and Why Do We Combine It With Radiation?

Androgen deprivation therapy (ADT), often just called hormone therapy, lowers testosterone, which is the fuel that prostate cancer cells use to grow. For decades, large randomized trials have shown that for high-risk prostate cancer, adding ADT to radiation improves not just cancer control but overall survival. Men live longer. This is one of the most consistently reproduced findings in all of prostate cancer care, and it is not in dispute.

What patients are rarely told is that ADT does two very different jobs when combined with radiation, and understanding the difference is the key to the whole duration question.

  • A systemic job. High-risk prostate cancer has a meaningful chance of having already shed microscopic cancer cells beyond the prostate, into lymph nodes or bone, that are too small to see on any scan. Radiation only treats what sits in its path. ADT circulates through the entire body and suppresses these microscopic deposits. This is the part of ADT’s benefit that radiation cannot replicate, no matter how high the dose.

  • A local job. ADT also makes the cancer cells inside the gland more vulnerable to radiation, a phenomenon called radiosensitization. By lowering testosterone, ADT impairs the cancer cell’s ability to repair the DNA damage that radiation inflicts, and it shrinks the tumor before treatment. A given dose of radiation ends up killing more cancer than it otherwise would.

That distinction is the entire reason this article exists. A brachytherapy boost can take over much of the local job, because it delivers such an enormous radiation dose that the cancer in the prostate is going to be sterilized regardless. It cannot take over the systemic job. Almost everything that follows is a consequence of that one idea.

Where the “18 to 36 Months” Recommendation Came From

The long ADT durations written into the guidelines were established by a series of excellent randomized trials. But nearly all of them studied external beam radiation alone, without a brachytherapy boost.

The classic trials (EORTC 22863, RTOG 85-31, RTOG 9202) first proved that long-course ADT added to external beam radiation improved survival in high-risk and locally advanced disease. Later trials refined the duration. EORTC 22961 compared 6 months with 36 months and favored the longer course. The Spanish DART01/05 GICOR trial compared roughly 4 months with 28 months of ADT even when using dose-escalated external beam radiation of 76 to 82 Gy, and still found that the longer course improved cancer control and survival in high-risk men. A Canadian trial (PCS IV) later showed that 18 months gave essentially the same survival as 36, which is how 18 months became the common high-risk anchor.

The lesson from this era is sound and worth respecting: with external beam radiation, even when you escalate the dose, longer ADT helps. That is exactly why the guidelines land on 18 to 36 months.

But notice what every one of those trials has in common. None of them used a brachytherapy boost. The recommendation we apply to brachytherapy patients today was, in effect, borrowed from the external beam world and never specifically tested in ours.

What the MARCAP Data Added, and Why It Points Toward Brachytherapy

In recent years the MARCAP consortium, a large international effort led in part by Dr. Daniel Spratt and Dr. Amar Kishan that pooled individual patient data from many randomized ADT trials, sharpened the picture considerably.

Two of its lessons matter here:

  1. First, MARCAP showed that when ADT is given relative to radiation matters: prolonging the ADT given after radiation improved outcomes, while extending the ADT given only before and during radiation did not. The durable, survival-relevant benefit of ADT lives mostly in the period after the radiation is delivered.

  2. Second, and most important for us, the analysis found that the radiation technique changes how much ADT a man needs. It estimated that with external beam radiation the benefit of ADT kept accruing out to roughly 26 months, whereas for men who received a brachytherapy boost there was no clear benefit to extending ADT much beyond about 12 months.

This is precisely what the two-jobs framework predicts. The brachytherapy boost takes over so much of the local job that the long ADT tail, which was partly there to help radiation finish the job inside the gland, stops paying off. This was the first strong signal that the borrowed external beam recommendation overshoots for brachytherapy patients. The next piece of evidence tested it head-on.

The TRIP Trial: The Best Data We Have on This Exact Question

If you want to know how much ADT a high-risk patient needs specifically when getting brachytherapy plus external beam radiation, there is really only one randomized trial that asks that question directly. It is the Japanese TRIP trial (TRIGU0907), published in 2023.

TRIP enrolled 332 men across 37 Japanese centers, all with high-risk disease (Gleason score above 7, PSA above 20, or stage T2c–T3a), and about half had a Gleason score of 8 to 10. Every man received the same backbone: 6 months of ADT (3 months before and 3 months during radiation), an iodine-125 seed implant planned to 110 Gy, and then 45 Gy of external beam radiation. They were then randomly assigned to either no further hormone therapy (6 months total) or an additional 24 months of ADT (30 months total).

After a median of more than 9 years of follow-up, the difference between the two groups was remarkable mostly for how small it was:

  • Biochemical (PSA) failure at 9 years occurred in 10.4% of the short-course group versus 9.5% of the long-course group, with heavily overlapping confidence intervals.

  • There were exactly 24 deaths in each arm, and 9-year overall survival was 87.2% versus 85.9%.

  • Distant metastases, salvage treatment, and prostate-cancer death were all statistically indistinguishable between the arms.

In plain terms, adding two extra years of hormone therapy on top of a brachytherapy-based regimen did not improve cancer control or survival in these high-risk men.

There is a scientific caveat I always make about this trial, because it is real. TRIP was designed as a superiority trial. It was built to detect whether 30 months was better than 6 months, and it failed to show that. Strictly speaking, that is not the same as proving the two are equal, and the authors themselves call for a dedicated non-inferiority study.

But I think it is important to be clear-eyed about how strong this result is. This was not a case of the curves separating and the study being too small to reach significance. The outcomes were nearly superimposed, with identical mortality, across almost a decade.

The authors noticed that the two curves drifted apart in the first year, as testosterone recovered faster in the short-course men, and then merged again by year four, which they read as a sign that the high radiation dose, not the hormones, was doing the heavy lifting on local control. As a practical matter this is about as reassuring a “no meaningful difference” as oncology produces, and given the cost and difficulty of running a trial like this, it is unlikely anyone will repeat it.

The price of those extra two years was not trivial. In the long-course arm, hot flashes were far more common (40.7% versus 26.7%), and testosterone took much longer to recover (a median of 1.3 years after stopping ADT versus 0.6 years in the short arm), with fewer men recovering it at all by six years (71% versus 82%). Those are exactly the things that determine whether a man feels like himself again after treatment.

Not All High-Risk Disease Is the Same

One of the most useful things in the TRIP data is its subgroup breakdown, because it shows that “high-risk” is not one category.

  • For men with Gleason 8 (Grade Group 4) disease, biochemical failure at 9 years was about 9 to 12% regardless of whether they got 6 or 30 months of ADT. This is the group in whom a genuinely short course looks most justified: the systemic risk is real but moderate, and the brachytherapy boost handles the local disease.

  • For men with Gleason 9–10 (Grade Group 5), the story was different. These men failed at roughly 30 to 37% by 9 years, and crucially, the longer ADT course did not rescue them (the 30-month arm was, if anything, numerically worse, though the numbers are small).

I read this not as “Gleason 9–10 patients need longer hormones,” because TRIP shows extending ADT did not help them, but as a reminder that the highest-grade disease carries a systemic burden that neither a brachytherapy boost nor a longer conventional ADT course fully controls. That is the group where the more important modern question is whether to intensify systemic therapy (for example with the agents now used in very-high-risk and node-positive disease), and where I individualize the most rather than reflexively applying the “6 months is enough” conclusion.

A Note on Timing: TRIP Was Neoadjuvant, Which Is Worth a Second Look

Here is a subtlety for the more technically minded reader. In TRIP, the 6-month ADT backbone was given as 3 months before radiation and 3 months during it, and in the short arm there was no hormone therapy after radiation at all.

That is notable, because the MARCAP work from the external beam world suggested the opposite preference: that for a fixed short course of ADT, weighting it toward the period after radiation tends to outperform giving it before. TRIP got its excellent results using the very sequencing that looked weaker in the external beam setting.

How do I reconcile that? It reinforces the theme of this whole piece. The rules from external beam radiation do not transfer cleanly to brachytherapy, because the balance between ADT’s local and systemic jobs shifts once you deliver an ultra-high dose to the gland. With a boost, local control is so dominant that the precise timing of a short ADT course seems to matter less than it does with external beam alone.

I would not throw out the principle entirely, though. The biology behind giving hormones into the post-radiation window is real, and adjuvant ADT very likely still matters for the higher-risk men in whom the systemic job is paramount. The most accurate summary is that brachytherapy lets you shorten the total duration substantially, while the optimal sequencing of that shorter course in the brachytherapy setting is simply less settled than the duration is.

Why Brachytherapy Changes the Equation, and Why Quality Matters

The reason a boost lets you safely shorten hormone therapy comes back to dose. A well-placed seed implant delivers a radiation dose to the prostate far higher than external beam radiation can safely achieve, and higher dose means more local cancer cells killed.

The ASCENDE-RT trial showed this powerfully. Men who received a brachytherapy boost had a long-term biochemical control rate around 84 to 85%, compared with roughly 62% for men who received dose-escalated external beam radiation instead, with both groups on the same 12 months of ADT. The only thing that changed was substituting the boost for more external beam, and cancer control improved dramatically. In unfavorable intermediate-risk disease, boost regimens have produced long-term cure rates as high as 94%.

There is a way to put a number on the underlying mechanism. Radiation oncologists describe the total dose a treatment delivers using biologically effective dose (BED). Older work has shown that ADT meaningfully improves outcomes when the BED is below roughly 200, but stops adding much once the BED climbs above that, regardless of risk category.

A modern brachytherapy boost pushes the BED well past that threshold. In TRIP, the median delivered BED was about 217, and local recurrence was just 2.4%. The dose was high enough that the hormones had little local work left to do.

An Emphatic Note on Quality: I want to be emphatic about one point, because it is the load-bearing assumption of this entire argument. All of this holds only for high-quality brachytherapy. The outcomes in trials like ASCENDE-RT and TRIP were achieved at experienced centers with meticulous, intraoperatively planned, dosimetrically excellent implants and central quality review (in TRIP, the great majority of implants used real-time, computer-based intraoperative dose adjustment). A poorly executed implant does not deliver the dose advantage, and therefore does not earn the right to shorten ADT. The dose escalation is the whole reason a man can take fewer hormones, so the quality of the implant is not a side detail. It is the basis for everything. High-risk men deserve to be offered a brachytherapy boost, and they deserve to have it done by an experienced brachytherapist.

When the Cancer Is Most Aggressive: The Gleason 9–10 Data

A boost mostly proves itself on PSA control, so a fair man will ask whether it changes the outcomes that actually matter: whether the cancer spreads, and whether he survives it. For the most aggressive localized prostate cancers, Gleason 9 and 10 (Grade Group 5), there is a large dataset that speaks directly to that question, and it is one of the most compelling arguments for brachytherapy that I know of.

In 2018, Dr. Amar Kishan and a consortium of 12 centers published a study in JAMA of 1,809 men with Gleason 9–10 prostate cancer, comparing the three standard definitive treatments: radical prostatectomy, external beam radiation with ADT, and external beam radiation plus a brachytherapy boost with ADT. These are precisely the men in whom the choice of treatment should matter most, because their cancers are the most likely to spread and to take a life.

The results were striking. At 5 years:

  • The rate of death from prostate cancer was about 12% after surgery and 13% after external beam radiation, but only 3% after external beam plus a brachytherapy boost.

  • The rate of distant metastasis at 5 years was about 24% after either surgery or external beam radiation, but only 8% after the boost.

Put in terms of relative risk, the brachytherapy boost was associated with roughly a 60% lower risk of dying of prostate cancer and a 70% lower risk of developing metastases than either of the other two options. Surgery and external beam radiation, by contrast, produced essentially identical outcomes to each other.

Two details make this especially relevant to everything above. First, this was not a story about radiation versus surgery. External beam alone and surgery came out the same as each other; the one thing that separated the men who did dramatically better from everyone else was the addition of the brachytherapy boost. The local dose was the variable that moved survival.

Second, and remarkably, the brachytherapy-boost patients achieved these better outcomes while receiving only about half as much hormone therapy: a median of 12 months of ADT, compared with 22 months in the external beam group. They lived longer and spread less, on less hormone therapy. That is the entire thesis of this article, observed in the real world and in the most aggressive disease we treat.

I will be candid about the limits, because this was not a randomized trial. It was retrospective, and despite careful statistical adjustment, the surgery patients were younger, had lower PSA values, and likely had fewer other illnesses, all of which tend to flatter surgical results. Follow-up was relatively short, around 4 to 6 years, and the survival advantage of the boost was clearest in the first seven and a half years before the groups drew closer together. A randomized trial would settle the matter, but Gleason 9–10 disease is uncommon enough that one may never be done, which makes a dataset of this size and quality about as strong as the evidence is likely to get.

Taken together with ASCENDE-RT and TRIP, the message is consistent. For high-risk prostate cancer, up to and including the most aggressive cancers, adding a high-quality brachytherapy boost to external beam radiation and ADT is one of the most effective treatments we have, and it tends to call for less hormone therapy, not more.

An Honest Counterpoint

A careful reader, or a careful physician, should know that not every randomized trial points the same way. The Australian TROG 03.04 RADAR trial found that 18 months of ADT reduced distant progression compared with 6 months even in men who received a brachytherapy boost. That is the strongest randomized signal that longer hormones might still help boost patients.

I do not dismiss it, but two things temper it: in RADAR the radiation dose was not randomized (so healthier men may have selected into the boost groups), and it used a high-dose-rate boost rather than the low-dose-rate seed implant studied in TRIP. The fairest reading of the whole body of evidence is that a brachytherapy boost lets most high-risk men shorten ADT substantially, that the favorable end of high-risk (Gleason 8) is where that is clearest, and that genuine uncertainty remains at the highest-grade end. It is also worth remembering that PSA control is not a perfect stand-in for living longer, which is one more reason to individualize rather than treat any single trial as the final word.

What About Surgery? The “Avoid Hormones” Argument

Many high-risk men are told that the way to skip hormones altogether is to have surgery, since prostatectomy is typically done without ADT. This deserves an honest look, because the comparison is often presented too simply.

First, the surgical hormone data. Decades of trials testing hormone therapy before prostatectomy found that it shrinks the tumor and reduces positive surgical margins, but it did not improve survival, which is why it never became standard. More recently there is real interest in intensified hormone therapy around surgery. The large PROTEUS trial is testing the next-generation agent apalutamide plus ADT before and after prostatectomy for high-risk disease, with results expected in 2026, and a smaller single-arm study (Apa-RP) reported an encouraging 100% biochemical recurrence-free rate at two years, though without a comparison group. The point for patients is that the surgical world is actively studying whether to add hormones around surgery, not confidently doing away with them.

Second, and more important for a real decision: for genuinely high-risk disease, surgery often does not avoid hormones so much as delay them. A substantial fraction of high-risk men who have surgery will see their PSA rise afterward and will go on to need salvage radiation, very often combined with salvage ADT. The Gleason 9–10 study above showed this plainly: about a third of the surgery patients went on to receive salvage radiation and roughly a quarter received salvage systemic therapy, compared with essentially no local salvage and only about 5% systemic salvage among the brachytherapy-boost patients.

When that happens, a man ends up with the side effects of surgery, such as incontinence and erectile dysfunction, plus radiation, plus hormones, delivered in sequence and often adding up to more than he would have faced with definitive radiation up front. So “choose surgery to avoid hormones” can be misleading for high-risk cancer. The hormones frequently arrive anyway, just later, and stacked on top of more treatment.

None of this is an argument against surgery for the right patient. It is an argument for an honest comparison: a planned brachytherapy-based program with a short, defined course of ADT, versus a surgical path that for high-risk disease carries a real chance of becoming surgery, then radiation, then hormones over time.

So, How Much ADT Do You Actually Need?

Here is how I think about it:

  • For a man with high-risk prostate cancer receiving a high-quality brachytherapy boost plus external beam radiation, the best randomized evidence we have (TRIP) and the best pooled analysis (MARCAP) both support a shorter course of ADT than the guidelines reflexively recommend, on the order of 6 to 12 months rather than 18 to 36.

  • This is clearest at the more favorable end of high-risk, such as Gleason 8 (Grade Group 4) disease.

  • For the highest-grade disease, Gleason 9–10, the brachytherapy boost still appears to be the single best local treatment, as the Kishan data show, but longer conventional ADT did not improve outcomes for these men in TRIP. They fail at higher rates regardless, so the live question for them is whether to intensify systemic therapy, not whether to simply extend a standard hormone course. This is the group where I individualize the most.

  • The current guideline durations are not so much wrong as blunt. They were derived largely from external beam trials and are applied uniformly across all high-risk men, which tends to over-treat the man who has received an excellent brachytherapy boost.

The reason this matters is not abstract. Hormone therapy carries real costs: fatigue, hot flashes, loss of libido and sexual function, muscle loss, mood changes, and effects on metabolism and the heart. If a man can achieve the same cure with 6 to 12 months instead of 2 to 3 years, that is a meaningful improvement in his life, not a technicality.

The goal has always been the highest chance of cure with the fewest long-term consequences, and for high-risk men a high-quality brachytherapy boost is one of the most powerful tools we have for shortening, rather than lengthening, the hormone therapy they need.

The Bottom Line

High-risk prostate cancer is curable, and radiation combined with ADT is one of the most effective ways to cure it. But “how much ADT” is not a one-size-fits-all answer. The honest, data-driven position is that a well-executed brachytherapy boost should change the conversation about hormone duration, and that for many high-risk men, particularly those with Gleason 8 disease, a short course of hormones is supported by the best evidence we have.

Every man with high-risk prostate cancer deserves to have a brachytherapy boost offered as one of his options, performed by an experienced brachytherapist, and to have a frank conversation about how that choice can reduce the amount of hormone therapy he needs. Choosing a treatment for prostate cancer is a very personalized decision. I recommend that every man with prostate cancer meet with a urologist, an experienced radiation oncologist, and an experienced brachytherapist before deciding.

If you are in California or one of our other locations and would like to discuss your high-risk prostate cancer treatment options with one of Western Radiation Oncology’s physicians, please contact us here to schedule a consultation.

This article is for educational purposes and does not constitute individualized medical advice. Treatment decisions should be made in consultation with your own physicians.