Radiotherapy for large bowel cancer

Radiotherapy treats cancer by using high-energy rays which destroy the cancer cells, while doing as little harm as possible to normal cells.

Radiotherapy is usually used to treat cancer of the rectum. It is not normally used for cancer of the colon except very occasionally to relieve symptoms.

Early-stage bowel cancer

Adjuvant radiotherapy

Adjuvant radiotherapy is used to treat cancer of the rectum after surgery, if it is thought likely that there may still be tiny amounts of cancer cells left behind.

Neoadjuvant radiotherapy

If a tumour is large, radiotherapy can be given before surgery to shrink the tumour and make it easier to remove. This is known as neoadjuvant radiotherapy.

Chemoradiotherapy

Sometimes rectal tumours are treated with a combination of chemotherapy and radiotherapy. This is known as chemoradiotherapy. This treatment can be given before or after surgery. The chemotherapy and radiotherapy may be given at the same time or they may be given one after the other. Giving the treatments together in this way can help to improve their effect. However the side effects of chemoradiotherapy can often be worse than if you have the treatments on their own.

Radiotherapy for secondary cancer

If a bowel cancer has spread or come back (particularly in the pelvic area) after initial treatment, radiotherapy may be used to shrink the cancer. It also relieves symptoms such as pain.

How radiotherapy is given

Radiotherapy is usually given at a hospital outpatients clinic as a series of short daily treatments. The treatments are usually given each weekday with a rest at the weekend. How the treatment is given can vary a lot, depending on what is considered to be most effective for your cancer and best for you. The course may last for just one week or a few weeks. Your doctor will discuss your treatment, how it will be given and how long it will last, with you beforehand.

Planning your treatment

To ensure that you receive maximum benefit from your radiotherapy, it has to be carefully planned.

On your first visit to the radiotherapy department, you will be asked to lie under a large machine called a simulator, which takes x-rays and scans of the area to be treated. Sometimes a CT scanner can be used for the same purpose.

Treatment planning is a very important part of radiotherapy and it may take a few visits before the clinical oncologist (the doctor who plans your treatment) is satisfied with the result.

Marks may be drawn on your skin to help the radiographer, who gives you your treatment, to position you accurately and to show where the rays are to be directed. These marks must remain visible throughout your treatment but they can be washed off once your course is over.

At the beginning of your radiotherapy you will be told how to look after the skin in the area to be treated.

Treatment

Before each session of radiotherapy, the radiographer will position you carefully on the couch, either sitting or lying, and make sure that you are comfortable.

During your treatment, which only takes a few minutes, you will be left alone in the room, but you will be able to talk to the radiographer who will be watching you carefully from the next room.

Radiotherapy is not painful but you do have to be still for a few minutes while your treatment is being given.

Side effects

Radiotherapy to the bowel area can cause side effects, such as diarrhoea, feeling sick (nausea) and tiredness. It can also cause more specific side effects, such as inflammation of the bowel or bladder lining.

These side effects can be mild or more troublesome, depending on the strength of the radiotherapy dose and the length of your treatment, but they tend to get worse as the treatment goes on.

The side effects will usually continue until a week or so after the treatment has finished, and then will gradually start to improve. Your clinical oncologist will tell you what to expect and you can ask your radiographer for advice if side effects are becoming a problem for you.

Feeling sick

Some people may feel sick (nauseated) but this is usually mild and anti-sickness drugs, called anti-emetics, can usually control this effectively. If you don’t feel like eating, you can replace meals with nutritious, high-calorie drinks. These are available from most chemists and can also be prescribed by your GP.

Diarrhoea

Radiotherapy may irritate the bowel and cause diarrhoea.  Your doctor can prescribe drugs to reduce this.

Tiredness

As radiotherapy can make you feel tired, try to get as much rest as you can, especially if you have to travel a long way for treatment each day.

Skin reaction

The skin in the area that is being treated may become red and sore. Many people find that this is mild, but for some people the skin can become very sore and painful.

The nurses and radiographers will give you advice on how to look after your skin during treatment. If your skin gets very sore, soothing creams can be prescribed.

Inflammation of the bladder lining (cystitis)

Radiotherapy to the bowel may cause inflammation of the lining of the bladder. This can make you feel as though you want to pass urine often. You may also feel a burning sensation when you pass urine.

It helps to drink plenty of water and other fluids to make your urine less concentrated. Your doctor can prescribe a medicine which can make passing urine more comfortable.

These side effects generally continue for several weeks and then disappear gradually once the course of treatment is over. It is important to let your doctor know if they continue.

Possible long term side effects

In a small number of people, the bowel or bladder may be permanently affected by the radiotherapy. If this happens, the increased bowel motions and diarrhoea may continue, or you may need to pass urine more often than before.

The blood vessels in the bowel and bladder can become more fragile after radiotherapy treatment and this can cause blood to appear in the urine or in bowel movements. This can take many months or years to occur. If you notice any bleeding, it is important to let your doctor know so that tests can be performed and appropriate treatment given.

Infertility and impotence

Radiotherapy to the pelvic area is very likely to cause infertility in men and women. Men may find that they become impotent due to the effect of the radiotherapy on the nerves in the pelvic area.

These effects can be very distressing if they occur and it is important to discuss them with your doctor or specialist nurse, who can help you to find ways of dealing with them. CancerBACUP’s section on sexuality and cancer has advice on coping with impotence.