The side effects of radiation therapy for bladder cancer can be divided into the following.

Side effects during/soon after treatment (Early or ‘acute’ side effects)


Tiredness is not uncommon during radiation therapy and may be worse if you are having chemotherapy at the same time. This will improve a few weeks to a few months after the treatment is over.


Most people will notice the need to pass urine more frequently and stinging or burning when passing urine in the second half of their treatment. With the extra fluid given along with chemotherapy, this may be worse on some days compared to others through the treatment course.

Treatment can be delivered between two to seven weeks (Monday to Friday) depending on the goal of treatment and other factors. Keeping the urine dilute (drinking plenty of water) and using urine alkylising agents, e.g. Ural, can help reduce stinging and burning when passing urine.

The bowels may also be affected temporarily with increased gas and/or diarrhoea or mild change in bowel habit. This is because some portions of bowel may be within the field receiving radiation. Again, these early side effects will almost certainly settle back to normal a few weeks after treatment is completed.

Keeping well hydrated and using medication to slow bowel activity (if prescribed by your doctor) can help this. Sometimes diet might need to be modified.

Side effects well after treatment (Late or long-term side effects)

The bladder sometimes becomes smaller in volume after radiation therapy, especially if it is small to begin with – this means that you may need to pass urine more frequently over the long term. This is why radiation therapy may not be the best option for patients who have very poor bladder function at presentation. If the bladder is working well before treatment, then this is not likely to be a problem.

A change in bowel habit is not uncommon post bladder radiation therapy and may manifest as a desire to use the bowels more frequently or be more constipated. Any exposure to radiation increases the risk of a second cancer developing in that area, usually decades later. This risk is not entirely attributable to radiation received as part of your treatment. All X-rays and scans received over your lifetime contribute to this risk, as does unavoidable exposure to environmental radiation. The risk of a cancer being caused by radiation therapy is in the order of 0.5 – 1% at 10 years.

Information and Guidance

Radiotherapy Treatment Process

Click below for a video that shows the external beam radiotherapy treatment process.