How five-session SABR compares with seed and HDR brachytherapy for prostate cancer: suitability, side effects, outcomes and the NHS route.
Key takeaways
Five-fraction radiotherapy is a form of SABR. It gives external beam radiation in five sessions over one to two weeks. Brachytherapy places the radiation source inside the prostate, either as permanent seeds (LDR) or through temporary implants (HDR).
Both are well established for localised prostate cancer. The choice usually turns on your risk group, prostate size and urinary flow, whether you have had prostate surgery before, and how each option fits your life.
In the UK-led PACE-B trial, five-fraction SABR gave cancer-control results at five years that were no worse than several weeks of conventional radiotherapy, with low side effects in both groups.
Stereotactic radiotherapy in five sessions is now offered on the NHS for suitable patients. Brachytherapy has been used in the UK for many years, and I perform both LDR and HDR forms regularly.
Neither option is better in the abstract. The right treatment is the one that matches your cancer and your circumstances, decided with your oncologist and urologist.
This article is general information. It cannot tell you which treatment is right for you. That decision needs a specialist who knows your case.
When patients weigh up five-fraction radiotherapy vs brachytherapy, they are usually choosing between two quite different ways of giving the same kind of treatment for localised prostate cancer. One is five-fraction radiotherapy, a course of five high-precision stereotactic (SABR) radiotherapy sessions spread over one to two weeks. The other is brachytherapy, where radiation is delivered from inside the prostate itself. Both aim to control the cancer while sparing the healthy tissue around it. They simply get there by different routes.
Most pages online explain one treatment or the other, or compare radiotherapy with surgery. Very few set these two radiation options side by side in plain terms. That is what this guide does. It is written for people in the UK making this choice, and for the partners and families helping them think it through. If it helps to step back first, my overview of prostate cancer and the range of external beam radiotherapy options may be a useful starting point.
In the UK, about 1 in 8 men will be diagnosed with prostate cancer in their lifetime. Prostate cancer can develop in anyone who has a prostate, which includes some trans women and non-binary people as well as men. The treatment principles here apply regardless of how you identify.
Before we start
This article informs a decision. It does not make it. Your risk group, your scans, your prostate size and your general health all shape what is suitable, and only your clinical team can weigh those together. Use this to ask better questions, not to conclude on your own.
The shared foundations of both treatments
Radiotherapy treats cancer with carefully targeted radiation. It damages cancer cells so they cannot keep dividing. For prostate cancer, it is one of the main options that aim to cure, alongside surgery, and for many people the outcomes are similar. What differs between the two options below is not whether radiation is used. It is how the radiation is delivered, and over what timescale.
External beam radiotherapy in brief
External beam radiotherapy is aimed at the prostate from a machine outside the body. Traditionally this meant a small dose given daily over seven or eight weeks. Modern technique allows a larger dose in each session, so the whole course finishes far sooner. Giving fewer, larger sessions is called hypofractionation. The shortest schedules, of around five sessions, are called ultra-hypofractionation or SABR. More on that shortly.
Brachytherapy in brief
Brachytherapy puts the radiation source inside the prostate, so the dose falls away sharply just beyond the gland. That short range is its defining feature. It comes in two forms, and the difference between them matters for the comparison, so it is worth being clear about both.
The two types of brachytherapy: LDR and HDR
People often use brachytherapy as if it were one thing. In practice, there are two distinct approaches, and they feel quite different as a patient. Over a typical year, I carry out around 400 brachytherapy procedures using both techniques, so the choice between them is one I talk through often.
Low dose rate (LDR): permanent seeds
In LDR brachytherapy, tiny radioactive seeds, each about the size of a grain of rice, are placed permanently into the prostate through fine needles, guided by ultrasound. This is usually a single day-case procedure under anaesthetic. The seeds give off radiation over weeks to months and then become inert. Because the source stays in the body for a time, there are some short-term precautions around close contact with young children and pregnant women, which your team will explain.
High dose rate (HDR): temporary implants
In HDR brachytherapy, thin catheters are placed into the prostate, and a radiation source is passed through them for a few minutes at a time, then removed. Nothing radioactive stays in the body afterwards, so there are no ongoing radiation precautions. HDR may be given on its own or combined with a short course of external beam radiotherapy, particularly for higher-risk disease.
Both forms are day-case or short-stay procedures. Both need an anaesthetic and precise image guidance. The seeds-versus-catheters distinction is one of the practical points people weigh when comparing brachytherapy with a course of external sessions.
What five-fraction radiotherapy (SABR) really involves
Stereotactic radiotherapy, also called SABR or SBRT, is external beam radiotherapy delivered with millimetre precision. That precision lets a high dose sit on the prostate while limiting the dose to the bladder and bowel around it. Because each session delivers more, the whole treatment can finish in around five sessions rather than dozens. In a UK setting, a typical schedule is 36.25 Gy given in five fractions over one to two weeks, often using a system such as CyberKnife or a modern linear accelerator.
The appeal is straightforward. Five hospital visits over a fortnight is a very different commitment from daily attendance for nearly two months. For someone working, caring for others, or travelling a distance to the cancer centre, that difference is not a small detail. It is often the deciding factor once the clinical options are judged to be equal.
How five-fraction radiotherapy is kept accurate
Delivering a high dose in so few sessions depends on knowing exactly where the prostate is each day. Several things make that possible, and not everyone needs all of them. The tools I use most often include:
- Fiducial markers. Small metal markers are placed into the prostate beforehand, usually under local anaesthetic so that the gland can be tracked precisely during each session.
- MRI or CT guidance. Detailed scans are used to plan and check the treatment. For selected patients, I also use MRI-guided radiotherapy on an MR-Linac, which lets us see soft tissue clearly and adjust the plan on the day.
- A rectal spacer. In some cases, a soft gel, such as SpaceOAR, is injected between the prostate and the rectum. It pushes the bowel out of the high-dose area and can lower bowel side effects.
You can read more about how MRI-guided treatment adds an extra layer of accuracy for suitable patients.
Five-fraction radiotherapy vs brachytherapy: how they compare
Here is the comparison most pages skip. The two treatments are more alike in their results than they are in their experience. The honest summary is that, for suitable patients, the cancer-control outcomes are broadly similar. The choice is shaped by suitability, side-effect profile and practicality, rather than by one being clearly better.
The patient experience
Five-fraction SABR means no surgical implant. You attend for five outpatient sessions. Each lasts a matter of minutes on the couch once set-up is done, and you go home the same day with nothing left in the body. Brachytherapy means a day-case procedure under anaesthetic to place seeds or catheters. LDR leaves permanent seeds and brief contact precautions. HDR leaves nothing behind. Some people strongly prefer to avoid an implant procedure. Others prefer a single procedure to five separate visits. No answer is right for everyone.
Cancer control
Both approaches produce high rates of cancer control in carefully selected patients with localised disease. Brachytherapy has decades of long-term data behind it. Five-fraction SABR now has strong trial evidence too, which we look at in the next section. A 2026 pooled analysis in intermediate-risk disease found that SBRT was associated with lower biochemical failure than HDR brachytherapy. This is a specific finding in a specific group, not a blanket ranking of one treatment over the other.
Side effects
The side-effect profiles overlap heavily. Both can cause urinary symptoms, such as needing to pass urine more often or more urgently, a slower flow, and some discomfort. Both can cause bowel symptoms, such as looser or more frequent motions and, occasionally, a little bleeding. Most of these settle with time. The balance of urinary versus bowel effects can differ slightly between techniques and between individuals. That is one reason your own anatomy and urinary flow feed into the recommendation.
Suitability
This is where the real difference lies. A large prostate, a poor urinary flow, previous prostate surgery such as a TURP, or certain anatomical factors can make brachytherapy less suitable. Sometimes these same factors make SABR the better-tolerated option, and sometimes the reverse is true. Risk group matters too. Some higher-risk cancers are treated with a combination of external radiotherapy and a brachytherapy boost, rather than either alone. Suitability is genuinely individual, and it is decided on your scans and measurements, not on preference.
What the UK evidence shows: the PACE-B trial
The reason five-fraction radiotherapy is now a mainstream option in the UK is largely down to a trial called PACE-B, led from the UK and run across centres in the UK, Ireland and Canada. It is worth understanding, because it changed practice. It is also the kind of question I am asked about often, so here is what it found.
PACE-B randomly assigned men with low- or intermediate-risk localised prostate cancer to one of two groups. One had five-fraction SABR, 36.25 Gy over one to two weeks. The other had a conventional or moderately shortened course of external beam radiotherapy over four to seven and a half weeks. At five years, 95.8% of the SABR group and 94.6% of the conventional group were free from biochemical or clinical failure. In plain terms, the shorter course was no worse at controlling the cancer.
Side effects were low in both groups. Five-fraction SABR showed a somewhat higher rate of urinary side effects and similar bowel side effects compared with the longer course, but the overall rates were modest. This is the kind of high-quality evidence that supports offering five sessions in place of many. It is why the approach has moved from research into routine care for suitable patients.
What this does and does not tell you
PACE-B compared five-fraction SABR with longer external beam radiotherapy, not directly with brachytherapy. It also studied low- and intermediate-risk disease without hormone therapy. It is strong evidence that five sessions can replace several weeks. It is not, by itself, a verdict on SABR versus brachytherapy for every patient. Trials comparing SABR and brachytherapy approaches more directly are ongoing.
Five-fraction radiotherapy vs brachytherapy: who suits which?
The following is a general guide to the factors your team considers when weighing five-fraction radiotherapy vs brachytherapy for your case. It is not a checklist you can score yourself against, and there are exceptions to every point. The main things I weigh up are:
- Risk group. Both are used for low- and intermediate-risk localised disease. Some higher-risk cancers are treated with external radiotherapy plus a brachytherapy boost, and sometimes with hormone therapy alongside radiotherapy.
- Prostate size. A very large prostate can make seed brachytherapy technically harder and may favour an external approach, though this is assessed one person at a time.
- Urinary function. A weak urine flow or significant urinary symptoms before treatment can influence which option is likely to be better tolerated.
- Previous surgery. Prior prostate surgery, such as a TURP for an enlarged prostate, can affect whether brachytherapy is suitable.
- Practical fit. Distance from the centre, work and caring responsibilities, and your own feelings about an implant procedure versus a short course of visits all count once the clinical options are judged equal.
If two options are genuinely equal for your cancer, your preference matters and should be heard. If they are not equal, your team will tell you why one is recommended.
Side effects and life after treatment
Whichever route you take, it helps to know what to expect in the weeks and months afterwards, and what tends to settle.
In the short term
Urinary symptoms are common early on. You may pass urine more often, more urgently, or with a weaker flow, and there may be some stinging. Bowel changes can include looser or more frequent motions, and occasionally a small amount of bleeding. These usually improve over the following weeks. Tiredness is also common, particularly towards the end of a course.
Erectile and sexual function
Radiotherapy of any kind can affect erections, and the risk tends to build over the years after treatment rather than appearing all at once. This is a real consideration for many people, and a fair question to raise directly with your oncologist, including what support and treatments are available if it happens. It is covered far too briefly on most pages, so do ask about it. My guide to erectile dysfunction after prostate cancer treatment goes into more detail.
Longer-term follow-up
After treatment you will have regular PSA blood tests to watch for any sign of the cancer returning. A rising PSA does not automatically mean the treatment failed, but it prompts a closer look. If cancer does come back after radiotherapy, further options may be possible. These include salvage treatments and, in selected cases, Lutetium PSMA therapy, and they are considered case by case.
Getting treated in the UK: the practical route
This is the part almost no page covers, and it is often what people most want to know once they have grasped the clinical picture.
On the NHS
Both brachytherapy and five-fraction stereotactic radiotherapy are available on the NHS for suitable patients, though not every hospital offers every technique. Brachytherapy and SABR tend to be delivered at specialist cancer centres. Your route usually runs from your GP or diagnosis, to a urologist and oncologist, then to a multidisciplinary team discussion where your case is reviewed, and the suitable options are agreed. You can, and should, ask which options are available to you and where they would be delivered.
Considering private treatment
Some people choose private treatment to reach a particular technique or centre sooner, or to see a specific consultant. If you are thinking about this, it is reasonable to ask about the likely timeline, which centres offer the technique, who would be responsible for your care, and the costs involved. Prices vary by treatment, centre and individual circumstances, so ask for a clear written estimate rather than relying on a headline figure.
Questions worth asking your team
A short list of questions can make an appointment far more useful. You might ask:
- Am I suitable for both five-fraction SABR and brachytherapy, or is one recommended for me, and why?
- What are the specific side-effect risks in my case, including for urinary and sexual function?
- How many sessions or procedures would each option involve, and over what period?
- Where would the treatment be delivered, and how experienced is the centre with it?
- What follow-up will I have, and what happens if my PSA rises later?
How to weigh the choice for yourself
It is tempting to look for the single best treatment. For localised prostate cancer, that is usually the wrong question. For a person whose cancer suits either option, the better question is which trade-offs fit your life and your priorities. That might be a short course of external sessions with nothing left in the body, or a day-case implant procedure. Both are backed by good evidence. Neither is a compromise.
Take the recommendation your team gives seriously, because it rests on details of your case that general information cannot see. Where there is genuine choice, weigh it openly with them, and permit yourself to ask the awkward, practical questions. This is your decision to understand, even if the clinical judgement guiding it is theirs.
Frequently Asked Questions
In five-fraction radiotherapy vs brachytherapy, is one better?
Neither is better in general. For suitable patients with localised prostate cancer, cancer-control outcomes are broadly similar. When people compare five-fraction radiotherapy vs brachytherapy, the choice is shaped by risk group, prostate size and urinary flow, whether you have had prostate surgery before, the side-effect profile, and how each option fits your life. Your oncologist and urologist decide suitability from your scans and measurements.
What is five-fraction radiotherapy for prostate cancer?
It is a form of stereotactic radiotherapy, or SABR. It delivers external beam radiation with high precision in five sessions over one to two weeks, rather than the older schedule of daily treatment for seven or eight weeks. A typical UK dose is 36.25 Gy in five fractions.
What is the difference between LDR and HDR brachytherapy?
LDR (low dose rate) brachytherapy places permanent radioactive seeds into the prostate. They give off radiation for weeks to months and then become inert. HDR (high dose rate) brachytherapy uses temporary implants. A radiation source is passed through catheters for a few minutes and then removed, so nothing radioactive stays in the body.
In five-fraction radiotherapy vs brachytherapy, how many sessions are there?
Five-fraction SABR is five outpatient sessions over one to two weeks. Brachytherapy is usually a single day-case procedure under anaesthetic, placing either permanent seeds (LDR) or temporary implants (HDR). For higher-risk disease, brachytherapy is sometimes combined with a short course of external radiotherapy.
Is stereotactic radiotherapy available on the NHS?
Yes. Stereotactic radiotherapy in five sessions is offered on the NHS for suitable patients, following trial evidence that it is safe and effective. It is generally delivered at specialist cancer centres, and not every hospital offers it, so ask which options are available to you and where.
What did the PACE-B trial show?
PACE-B, a UK-led phase 3 trial, found that five-fraction SABR gave cancer-control results at five years that were no worse than several weeks of conventional radiotherapy for low and intermediate-risk localised prostate cancer. At five years, 95.8% of the SABR group and 94.6% of the conventional group were free from biochemical or clinical failure, with low side effects in both.
