Radiotherapy for rectal cancer

Radiotherapy uses high energy rays to kill cancer cells. Doctors don't often used to treat cancer in the large bowel (colon cancer). But they often use it to treat cancer that started in the back passage (rectum). Usually, you have this treatment at the same time as 5FU (fluorouracil) chemotherapy. The chemotherapy makes the cancer cells more sensitive to radiation.

To try to cure rectal cancer, you may have radiotherapy

• Before surgery (preop radiotherapy)
• After surgery (postop radiotherapy)

Another page in this section tells you about radiotherapy to treat the symptoms of advanced bowel cancer.

Doctors use radiotherapy before surgery to

• Lower the risk of the cancer coming back after surgery
• Shrink tumours and make them easier to remove completely

If your tumour can be operated on, you are likely to have a short course of 5 radiotherapy treatments in the week before surgery. This will kill many of the cancer cells. And the treatment also makes it less likely that any cancer cells will spread at the time of your surgery. You may have 5FU (fluorouracil) chemotherapy at the same time as the radiotherapy. Doctors call chemotherapy and radiotherapy given together chemoradiation.

If you have a large tumour, you may need a longer course of treatment before surgery. The treatment may last up to 5 weeks. You may have 5FU chemotherapy at the same time. You usually have surgery a few weeks after this sort of radiotherapy, to give the tumour time to shrink.

A newer treatment for rectal cancer is high dose internal radiotherapy before surgery. This treatment is called brachytherapy. You normally have a sedative before the procedure to help you to relax. The doctor gently pushes a tube containing radioactive material through your anus into your rectum and places it close to the tumour. It is left in place for a while to deliver the correct dose of radiation to the cancer. The aim is to shrink the tumour so that it is easier to completely remove it. You have surgery a few weeks later.

Results from studies seem to show that people who have internal radiotherapy are less likely to need a colostomy than people who have external radiotherapy. But it is not clear whether internal radiotherapy helps people to live any longer. The National Institute for Health and Clinical Excellence (NICE) guidelines say the procedure is safe and works well enough to be used for rectal cancer. But we need further research to see how well it works. 

Everyone who has internal radiotherapy for rectal cancer treatment must be closely monitored afterwards. Possible side effects of the procedure include making a hole in the rectum or bladder, tightening (stenosis) of the back passage, or a hole (fistula) developing between the rectum and the bladder or vagina.

If you haven't had radiotherapy before your operation, your surgeon and cancer specialist may want you to have some external radiotherapy afterwards if

• Your cancer was difficult to remove
• Your surgeon thinks some cancer cells may be left behind
• Your cancer had grown through the bowel wall or spread to nearby lymph nodes

Radiotherapy after surgery is called adjuvant radiotherapy (pronounced ad-joo-vant). You usually have this type of radiotherapy treatment over 4 to 5 weeks. You have treatment from Monday to Friday, so you have 20 to 25 treatments in total. Each individual treatment is called a fraction. Giving the treatment in small fractions reduces the side effects to healthy tissues. You may have chemotherapy with radiotherapy. Doctos call this chemoradiation.

Radiotherapy treatment is carefully planned. During your planning appointment, you may have a CT scan or may lie under a large machine called a simulator. This is so the doctor can see the cancer from all sides (3 dimensionally or 3D). The picture below shows a simulator.

Using information from the CT scan or simulator, your treatment team work out exactly where to give the treatment, in order to

• Target all of the tumour and a border of tissue around it, where there are most likely to be cancer cells
• Avoid as much of the surrounding healthy body tissue as possible

For external radiotherapy, you may have marks made on your skin during the planning session. The radiographer uses these skin marks to line up the radiotherapy machine every day when you have your treatment. Don't worry if they wear off a bit. Your radiographer can draw them again. They need to be very accurate so don't try to draw them on again yourself. Sometimes the radiographer replaces the skin marks with a few pin prick tattoos.

You have radiotherapy in the hospital radiotherapy department.

Internal radiotherapy (brachytherapy) usually just takes one or two sessions.

For external radiotherapy, you usually have treatment once a day from Monday to Friday. You then have a rest over the weekend. The treatment before surgery for rectal cancer lasts from 1 to 5 weeks, depending on the size and type of your cancer and the hospital treating you.

If you are having radiotherapy after surgery, the course of treatment is usually 4 to 5 weeks, but may be up to 6 or 7 weeks long.

With external radiotherapy, the actual treatment only takes a few minutes. The radiographer positions you on the treatment table and makes sure you are comfortable. You will be left alone while you have your treatment but the radiographers can hear you through an intercom. You can talk to them or ask them questions.

Radiotherapy doesn't hurt. You won't be able to feel it but you need to lie very still for the few minutes that you have your treatment.

Radiotherapy doesn't make you radioactive. It is perfectly safe to be with other people, including children, throughout your course of treatment.

To find out more about radiotherapy, look at our main radiotherapy section. It tells you about

• What radiotherapy involves
• How your treatment is planned
• Possible side effects

There are books and booklets about radiotherapy, some of which are free. Look in the treatment reading list for details.

We also have information about the latest research into radiotherapy for rectal cancer.