Side effects of bowel cancer radiotherapy

You may get some side effects while you are having the treatment. The effects usually start gradually during the course of treatment. They may carry on for a week or two after the treatment ends. These side effects may include

• Tiredness
• Diarrhoea
• Feeling sick
• Passing urine more often
• Sore skin in the treatment area

Tiredness

You may find that you become more and more tired as your treatment goes on. This is very common with radiotherapy. Tiredness can be an effect of the treatment itself.  And it can be partly due to travelling back and forth to hospital each day for treatment. 

Don't be afraid to rest if you feel you need to. It is good to try and get some gentle exercise each day. But if you feel that you want to have a lie down, it is best to do that.  We have more information about coping with tiredness on this link.

Diarrhoea

Your doctor can give you medicines to reduce diarrhoea, so do tell your doctor or specialist nurse if you have this side effect. There is information about dealing with diarrhoea in our section about bowel problems with cancer. It is important to drink plenty of fluids if you have diarrhoea.

Feeling sick

You may not feel like eating or drinking much if you are feeling sick. But it is important to drink plenty of fluids. If you are having trouble eating, try having high calorie drinks. You can get the drinks on prescription or buy them from your chemist. There is information about dealing with sickness in our section about coping physically.

Passing urine more often

The rectum is very close to the bladder. So, bowel radiotherapy can irritate the lining of the bladder. You may feel as though you have a bladder infection (cystitis). You may feel as though you want to pass urine all the time, but when you go there isn't much there. You may have a burning pain when you do pass urine.

Try to drink plenty of fluids. Many people think that drinking cranberry juice can be helpful with bladder problems. Cranberry juice can increase the effects of warfarin (a blood thinner or anticoagulant). So you shouldn't drink cranberry juice if you are taking warfarin.

Your bladder inflammation will settle down after the treatment is over. But let your doctor know if you have any pain when passing urine. It could be a sign that you have an infection that needs antibiotic treatment.

Sore skin

Radiotherapy can make the skin sore. The skin round the anus is very sensitive. It may get quite red and sore during your radiotherapy treatment. Treat the skin very gently during treatment and for a few weeks afterwards. Wash with plain water and simple soaps, such as baby soap. Gently pat the skin dry with a soft towel.

Your doctor, nurse or radiographer will give you some creams to use to protect your skin and help it heal quickly. Don't use perfumed or medicated soaps or any other lotions unless you have discussed them first with your specialist, radiotherapy nurse, or radiographer. 

You may have difficulty sitting comfortably for a while. Try using a soft cushion. You can also ask for help and advice from your radiotherapy nurse. After your treatment is over, the soreness will gradually get better over a few weeks.

As well as short term side effects while you are having treatment, radiotherapy can cause long term side effects in some people. Your doctor will plan your treatment carefully to make sure you have as few side effects as possible. But radiation causes more side effects in some people than others.

Not everyone who has bowel cancer radiotherapy will have long term side effects. Some people get back to a normal life quickly after their treatment. But for some people the short term effects of treatment may continue and become long term effects. For other people, the short term effects may get better but then signs of long term changes to the bowel or bladder may begin. These can start from a few months to a couple of years after finishing your course of treatment. The long term effects of radiotherapy to the bowel include

• Diarrhoea
• Needing to have your bowels open very often
• Poor absorption of food from your gut, leading to weight loss

Radiotherapy can also affect the bladder, causing

• Leaking of urine (incontinence)
• The bladder wall to become less stretchy, so you have to pass urine more often
• Fragile blood vessels to form in the wall of your bladder, causing blood in the urine

It may also affect your sex life, causing

• Early menopause
• Difficulty getting an erection
• Loss of fertility for men and women
• Dryness and shrinkage of the vagina making sex painful

Talk to your doctor if you think you have developed any of these side effects. There are ways of reducing and managing them. Sometimes other conditions such as infections can cause similar symptoms to the long term side effects of bowel cancer radiotherapy. You can usually have treatment for the condition causing the effects.

You may feel very embarrassed to talk to doctors or nurses about effects such as diarrhoea, narrowing of your vagina or leaking of urine (incontinence). But doctors and nurses deal with these things all the time, so you don't need to feel embarrassed. If you tell them about any problems you have, they can find ways of helping you to deal with them.

In our radiotherapy section, you can find more detailed information about radiotherapy and its side effects. There is information about dealing with the side effects of pelvic or stomach radiotherapy which you may find helpful.

There is information about coping with early menopause, vaginal dryness, and difficulty getting an erection, in our sex and sexuality section.