Radiotherapy can affect the bladder, bowel and sexual function. Side effects may include urinary frequency, urgency, discomfort passing urine, bowel looseness, rectal urgency, rectal bleeding, fatigue and erectile dysfunction.

Some side effects occur during or soon after treatment. Others may develop months or years later.

PSA follow-up after radiotherapy is different from PSA follow-up after surgery because the prostate remains in place.

Surgery after radiotherapy, if needed later, can be more complex because of scarring and tissue changes.

Prostate size and urinary symptoms

Prostate size and existing urinary symptoms matter when considering radiotherapy.

Some men with prostate cancer also have lower urinary tract symptoms, often called LUTS. These may include:

Passing urine frequently
Getting up at night to pass urine
Urgency
Slow flow
Hesitancy
Straining
Incomplete emptying
Urinary retention

A large prostate or significant urinary symptoms can make radiotherapy planning more complicated. Radiotherapy can irritate the bladder and prostate, and in some men urinary symptoms may worsen during or after treatment.

This is one area where surgery can sometimes offer an advantage. Radical prostatectomy removes the prostate and may also treat obstruction from the prostate at the same time. In men with troublesome LUTS caused by prostate enlargement, surgery may improve the obstructive element because the prostate is removed.

Radiotherapy does not remove the prostate. If a man already has poor flow, retention, severe nocturia or significant bladder outlet obstruction, this needs careful assessment before treatment.

Channel TURP before radiotherapy

Some men with severe urinary obstruction may need a procedure called a channel TURP before radiotherapy.

A TURP involves removing tissue from the inside of the prostate to improve the urinary channel. A channel TURP is usually a more limited version, intended to improve flow or relieve obstruction rather than remove the whole prostate.

This may be considered if urinary symptoms are severe, if the patient is in retention, or if there is concern that radiotherapy could worsen obstruction.

However, TURP before or after radiotherapy can have risks, including bleeding, scarring, urinary leakage, bladder neck narrowing and healing problems. Timing matters. This should be planned carefully by the urology and oncology teams.

Bowel function

Bowel history is important before radiotherapy.

The rectum sits directly behind the prostate, so radiotherapy can affect bowel function. Men with pre-existing bowel conditions may need more detailed discussion before treatment.

Possible bowel side effects include:

Loose stools
Rectal urgency
Mucus
Bleeding
Discomfort
Frequency
Rare longer-term bowel problems

Modern radiotherapy planning aims to reduce dose to the rectum, but bowel side effects cannot be completely removed.

Rectal spacers insert gel between the rectum and prostate to try and avoid this problem but not everyone can have a spacer and it requires specialist input

Sexual function

Radiotherapy can affect erections and sexual function.

This may happen gradually rather than immediately. Some men notice erectile dysfunction months or years after treatment. The risk is higher if hormone therapy is also used.

Radiotherapy may also reduce ejaculation, change orgasm and affect fertility.

Baseline erectile function matters. Age, diabetes, vascular disease, smoking, medication and testosterone levels can all influence sexual recovery and long-term function.