Radiotherapy for rectal cancer
Radiotherapy treats cancer by using high-energy rays to destroy the cancer cells, while doing as little harm as possible to normal cells.
Radiotherapy only treats the area of the body that the beams are aimed at. Radiotherapy is often given in combination with chemotherapy, which is called chemoradiotherapy. The chemotherapy makes the cancer cells more sensitive to radiotherapy.
Radiotherapy doesn’t make you radioactive and it’s perfectly safe for you to be with other people, including children, throughout your treatment.
Early-stage rectal cancer
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Radiotherapy before surgery
Radiotherapy may be given before surgery to shrink a cancer and make it easier to remove. It also reduces the chance of the cancer coming back.
A short course of radiotherapy consisting of five treatments may be given over a week, just before the surgery.
If the cancer is large, a longer course of radiotherapy may be given, lasting for up to six weeks. This is usually given with chemotherapy (chemoradiotherapy), which can help make the radiotherapy more effective.
Following the course of radiotherapy, you’ll have to wait up to six weeks for the side effects to settle down before you can have the operation.
Radiotherapy after surgery
If radiotherapy wasn’t given before surgery, you may have it afterwards if:
the cancer was difficult to remove
some cancer cells may be left behind
the cancer had spread through the bowel wall or into nearby lymph nodes.
This type of radiotherapy may be given as treatment every weekday for 4–5 weeks.
Radiotherapy for secondary cancer
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Radiotherapy may be used to shrink the cancer if a rectal cancer has spread or come back after initial treatment (particularly in the pelvic area). It also relieves symptoms such as pain.
There are some specialised radiotherapy techniques that may be used when the cancer has spread to the liver.
One method is selective internal radiotherapy (SIRT). Another method is stereotactic radiotherapy (sometimes called cyberknife). Your doctor can discuss with you if these treatments will be suitable for you.
To make sure radiotherapy is as effective as possible, it has to be carefully planned by a clinical oncologist (a doctor who specialises in radiotherapy treatment for cancer).
Your treatment will be planned on your first visit to the radiotherapy department.
Usually, you’ll have a CT scan of the area to be treated. The radiographer may draw tiny marks on your skin. These marks must stay visible throughout your treatment, and permanent marks (like tiny tattoos) may be used. These are extremely small, and will only be done with your permission. It may be a little uncomfortable while they are done.
The radiographer will position you carefully on the couch at the beginning of each radiotherapy session, and make sure you are comfortable. During your treatment you’ll be alone in the room, but you can talk to the radiographer, who will watch you from the next room. Radiotherapy is not painful, but you have to lie still for a few minutes during the treatment.
How radiotherapy is given
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Radiotherapy for rectal cancer is usually given to you as an outpatient in the radiotherapy department, over a series of short daily treatments. The radiotherapy is given using equipment similar to a large x-ray machine. The treatments are usually given from Monday to Friday, with a rest at the weekend.
How the treatment is given varies, depending on your situation. The course may last for just one week or for a few weeks. Your doctor will discuss your treatment with you beforehand, including how it will be given and how long it will last.
Internal radiotherapy involves having a radioactive material (the source) placed close to or inside the tumour for a limited period of time. This is called brachytherapy. As with external radiotherapy, high-energy x-rays are used to kill the cancer cells.
High-dose rate (HDR) rectal brachytherapy
HDR rectal brachytherapy can be used in some cases before surgery if the cancer is in the middle or lower third of the rectum. It tries to shrink the tumour and reduces the need to remove the anus during surgery. Brachytherapy may be used in combination with external radiotherapy and surgery, or can be used on its own. Your doctor will discuss with you whether you‘re suitable for this treatment.
Before the treatment, the rectum needs to be emptied. This involves having a mini-enema, which is given in the radiotherapy department. Brachytherapy is given under a general anaesthetic, and the procedure lasts for about an hour.
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 how much treatment you receive.
They tend to get worse as the treatment goes on. The side effects will usually continue for a week or so after the treatment has finished, and then will gradually start to get better. 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.
Some people may feel sick (nausea) but this is usually mild, and anti-sickness (anti-emetic) drugs can usually control this.
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.
Radiotherapy may irritate the bowel and cause diarrhoea. Your doctor can prescribe drugs to reduce this.
Our section on eating problems has tips on coping with problems such as nausea and diarrhoea.
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.
You may find our section on coping with fatigue helpful.
The skin in the area being treated may become red and sore. Many people find this is mild, but for others, the skin can become very sore and painful. The nurses and radiographers can advise you 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 rectum 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 medicine to make passing urine more comfortable.
These side effects generally continue for several weeks and then disappear gradually once the course of treatment is over. Let your doctor know if they continue.
Possible long-term side effects of radiotherapy
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In some people, the bowel or bladder may be permanently affected by 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 make blood appear in the urine or in bowel movements.
It can take months or years before these side effects develop. If you notice any bleeding, it’s important to let your doctor know so that you can have tests and appropriate treatment.
Infertility and impotence
Radiotherapy to the pelvic area is likely to cause infertility. Men may find that they become impotent due to the effect of the radiotherapy on the nerves in the pelvic area. Women may find that sensations during sex are different.
These effects can be distressing, so it’s important to discuss them with your doctor or specialist nurse, who can help you find ways of dealing with them.
Our section on sexuality has helpful information about infertility and impotence.