Long-term side effects of prostate cancer radiotherapy

Awaiting medical review

This guide has not yet been reviewed or signed off by Dr Khan. It is published here for his review only and should not be treated as final medical information until that review is complete.

The short answer

Most bladder and bowel upset during radiotherapy settles within weeks. A minority of men live with lasting changes, and the pattern is specific rather than general: radiotherapy protects urinary continence far better than surgery does, but it is the only one of the three main approaches where bowel leakage kept increasing years afterwards.

In short

• Urinary leakage needing a pad affected 3% to 8% after radiotherapy, against 18% to 24% after surgery.
• Bowel leakage more than weekly reached 12% by year 12, double both other groups.
• Rectal bleeding, worse early on, had settled back to normal levels by years 7 to 12.
• 27% had erections firm enough for intercourse at 7 years, against 18% after surgery.
• Overall physical and mental health scores were similar whichever treatment men had.

The figures on this page come from ProtecT, a UK randomised trial of 1,643 men who were assigned between 2001 and 2009 to surgery, radiotherapy or active monitoring, then asked about their own symptoms every year for 12 years. Source: Donovan et al., NEJM Evidence, 2023.

If you are reading this before treatment, you are probably trying to work out what you are agreeing to. If you are reading it years afterwards, you may be wondering whether something you are living with is connected to radiotherapy you had a long time ago.

This guide answers both, using numbers men actually reported about themselves rather than what clinicians recorded on their behalf. Where the honest answer is that nobody publishes a reliable figure, it says so.

What counts as a long-term side effect of prostate radiotherapy?

This distinction matters because the two are often described together, which makes treatment sound far more damaging than the long-term evidence supports. Prostate Cancer UK puts the individual variation plainly, noting that side effects affect each man differently and that you might not get all of the possible ones.

It also cuts the other way. A few effects are barely noticeable at first and become more common as the years pass, which is easy to miss if you only look at results from the first year or two.

How likely are long-term urinary problems after radiotherapy?

By year 12, 7% of the radiotherapy group described urinary leakage as a moderate or severe problem. Prostate Cancer UK describes urinary incontinence after external beam radiotherapy as rare, which sits comfortably alongside those numbers.

Needing to pass urine at night is the more common lasting change. Getting up at least twice a night affected 48% of the radiotherapy group by year 12, close to the 47% among men on active monitoring, and higher than the 34% after surgery. The trial authors suggest removing the prostate probably relieved existing obstruction, which is why surgery looks better on this one measure.

Reassuringly, urinary symptoms interfered with quality of life somewhat or a lot for 5% to 7% of the radiotherapy group, the lowest of the three.

Will radiotherapy affect erections, and does that change over time?

That convergence is the part worth sitting with. Men who had no radical treatment at all ended up in a similar place, which suggests ageing accounts for a large share of what is often attributed to treatment alone.

Two things shape the early drop. Men in the ProtecT radiotherapy group also had hormone therapy beforehand, which suppresses sexual function in its own right, and Cancer Research UK notes that radiotherapy can damage the nerves involved in getting an erection. It also notes that erection problems are less likely in men under 65.

Treatment options exist and are worth asking about early rather than late. Cancer Research UK mentions that medicines such as sildenafil may help, and specialist services can discuss other approaches when tablets are not enough.

What happens to bowel function in the years after radiotherapy?

That finding deserves emphasis because it runs against the usual reassurance. Most side effects improve with time. This one did the opposite, and it only became visible because ProtecT kept asking the same men the same questions for 12 years.

Rectal bleeding behaved in the opposite way. It was worse in the radiotherapy group early on, then resolved, becoming similar to the other groups by years 7 to 12. Prostate Cancer UK notes that a tiny amount of blood is normal and not usually a cause for concern, though any new or persistent bleeding should always be checked.

Looser stools and the overall effect of bowel habits on quality of life were similar across all three groups in those later years. So the specific issue is leakage, not bowel disruption in general.

Practical help exists. Cancer Research UK mentions anti-diarrhoea medicines such as loperamide and bulking agents such as Fybogel, and many NHS trusts run late-effects clinics for exactly this.

What about lymphoedema, bone changes and second cancers?

Cancer Research UK puts the second-cancer risk the same way, saying a small number of men develop bladder cancer or cancer of the rectum after prostate radiotherapy, sometimes many years later.

We have deliberately not attached numbers to these. The organisations with the best access to the data have chosen not to, because the risk varies with technique, dose and how long a man lives after treatment, and a single figure would imply more precision than exists.

Do modern radiotherapy techniques change these odds?

There is a real caveat in the trial authors' favour here. Newer techniques did show less impact in the first year, and when treatment was given without hormone therapy. It was specifically among men who also had hormone therapy that the effects matched ProtecT.

The authors are candid that the long-term question is still open. They point to image guidance using MRI-linear accelerators and to hydrogel spacers as approaches that may reduce bowel toxicity over the longer term, and say this still needs investigating.

If you are choosing treatment now, this is a reasonable thing to ask your oncologist directly: what technique will be used, whether hormone therapy is part of the plan, and what that combination means for you specifically.

How do radiotherapy, surgery and monitoring compare over 12 years?

One caution about reading this table. Men on active monitoring did not simply avoid treatment: 59% of them had gone on to have a radical treatment by year 12, so that column is not a picture of untreated prostate cancer.

Which symptoms should prompt a call to your team?

Beyond that, these are worth raising rather than tolerating:

• Bowel leakage that is new or getting worse, given this is the effect ProtecT found increasing over time
• Urinary leakage that starts affecting daily life, even if it seemed manageable before
• Swelling in the legs or scrotum, which can indicate lymphoedema
• Erection difficulties you have not discussed, since options are wider than tablets alone
• Any symptom you have quietly assumed you have to live with, particularly if treatment was years ago

Late-effects services exist in many NHS trusts and a referral can come from your GP as well as your oncology team. If you have recently been diagnosed and are still weighing options, our guide on what to do after a cancer diagnosis covers the questions worth asking, and our prostate cancer guide covers the condition itself.

None of this is a reason to avoid radiotherapy. It is a highly effective treatment, and the trial that produced these numbers also found that overall physical health, mental health, anxiety and depression were similar whichever treatment men received. Knowing what to watch for is what makes the difference between a problem managed and a problem endured.

Guides like this are free, medically reviewed and paid for by supporters. Much of prostate cancer risk is influenced long before any treatment decision, and our prevention guide covers what the evidence actually supports.