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Anal cancer

Anal cancer

The anus is the name for the muscular area at the very end of the large bowel. It is the muscle which opens and closes to control bowel movements, and is where the bowel opens to the outside of the body. This muscle is also called a sphincter.

The most common type of anal cancer is squamous cell. Other rarer types are basal cell, adenocarcinoma and melanoma. This information deals with the treatment of squamous cell carcinoma.

Diagram showing the position of the anus

Diagram showing the position of the anus (d)

Causes of anal cancer

Cancer of the anus is rare. Less than 400 people are diagnosed with this type of cancer each year in the UK. It is slightly more common in women than in men. As with most cancers the cause of anal cancer is unknown.

It is known that anal cancer is more common in gay men. It is also more likely to develop in people who have had a particular virus infection called the human papilloma virus (HPV). The risk of having HPV increases with the number of sexual partners you have. Anal cancer is also more common in people who have a lowered immunity due to medical conditions, such as HIV. Cigarette smoking may also increase a person’s risk of developing anal cancer.

Signs and symptoms

The most common symptoms of anal cancer are bleeding from the rectum, and pain. Some people develop small firm lumps which may be confused with piles (haemorrhoids). Some people have discomfort, itching and a discharge of mucous (a jelly-like substance) from the anus. Faecal incontinence (a reduced ability to control bowel function) may also occur. Occasionally anal cancer can appear as an ulcerated area and may spread to the skin of the buttocks.

How it is diagnosed

Usually you begin by seeing your GP who will examine you and refer you to a specialist in bowel conditions (gastroenterologist). The doctor at the hospital will take your full medical history, do a physical examination and take blood samples to check your general health. Before the doctor can make a firm diagnosis of anal cancer a number of tests will have to be done.

Rectal examination  This is also sometimes known as a PR examination and is where the doctor examines your back passage with a gloved finger.

Biopsy  A small sample of cells is taken from the tumour so that it can be examined under a microscope. Usually this involves using either a special biopsy device (known as a punch biopsy) or the doctor can cut a small piece away from the tumour (known as an incisional biopsy). This can be done under local or general anaesthetic.

X-rays  These may be taken to show if there has been any spread of the cancer.

Ultrasound scan  A simple, painless scan which uses sound waves to form a picture of the inside of the abdomen.

CT (computerised tomography) scan  This is a more sophisticated type of x-ray which builds up a three-dimensional picture of the inside of the body. The scan is painless but takes longer than an x-ray (10–30 minutes). It may be used to identify the exact site of the tumour or to check for any spread of the cancer. Most people who have a CT scan are given a drink or injection to allow particular areas to be seen more clearly. Before having the injection or drink, it is important to tell the person doing this test if you are allergic to iodine or have asthma.

MRI (magnetic resonance imaging) scan  This test is similar to a CT scan, but uses magnetic fields instead of x-rays to form a series of cross-sectional pictures of inside the body. During the scan you will be asked to lie very still on the couch inside a metal cylinder. You will usually be given an injection to allow the pictures to be seen more clearly.

The test can take about 30 minutes and is completely painless, although the machine is quite noisy. If you don’t like enclosed spaces you may find the machine claustrophobic. You will be given earplugs or headphones and you can usually take someone with you into the room to keep you company. A two-way intercom enables you to talk with the people controlling the scanner.


The ‘stage’ of a cancer is a term used to describe its size and whether it has spread beyond its original site. Knowing the particular type and the stage of the cancer helps the doctors to decide on the most appropriate treatment.

Cancer can spread in the body, either in the bloodstream or through the lymphatic system. The lymphatic system is part of the body’s defence against infection and disease. The system is made up of a network of lymph glands (also known as lymph nodes) that are linked by fine ducts containing lymph fluid. Your doctors will usually check the nearby lymph nodes when staging your cancer.

  • Stage 1  The cancer only affects the anus and is smaller than 2cm in size. It has not begun to spread into the sphincter muscle.
  • Stage 2  The cancer is bigger than 2cm in size but has not spread into nearby lymph nodes or to other parts of the body.
  • Stage 3A  The cancer has spread to the lymph nodes close to the rectum, or to nearby organs such as the bladder or vagina.
  • Stage 3B  The cancer has either spread to the lymph nodes in the groin and pelvis, or to the lymph nodes close to the anus as well as nearby organs, such as the bladder or vagina.
  • Stage 4  The cancer has spread to lymph nodes in the abdomen or to other parts of the body, such as the liver.

If the cancer comes back after initial treatment, this is known as recurrent cancer.


Grading refers to the appearance of the cancer cells under the microscope and gives an idea of how quickly the cancer may develop. Low-grade means that the cancer cells look very like the normal cells. They are usually slow-growing and are less likely to spread. In high-grade tumours the cells look very abnormal, are likely to grow more quickly and are more likely to spread.


The main types of treatment used for anal cancer are a combination of radiotherapy and chemotherapy, which may be given at the same time or following one another. This combination of treatment is usually very successful. Surgery may be used, but is not often used as the first choice of treatment for anal cancer.


High-energy rays are used to destroy cancer cells, while doing as little harm as possible to normal cells. The treatment is often given for a few minutes each weekday for several weeks.

During the treatment period you may have changes in your bowel function such as diarrhoea, or passing wind: these side effects can sometimes be reduced by avoiding particular foods. Towards the end of the treatment period you may have blistering and soreness of the skin around the anal area, and possibly in the groin areas too. Extreme tiredness, or fatigue, is a common side effect of radiotherapy too.

These side effects usually decrease gradually once the treatment has ended, but it may take some months for skin changes to go back to normal. A small proportion of people find that their bowel function is permanently altered, and it is important to discuss this with your doctor as it is often possible to find ways of reducing any problems. Your doctor or a dietitian at the hospital can give you advicer.

Other potential side effects that can occur after radiotherapy for anal cancer include narrowing of the vagina (vaginal stenosis), and dryness. To help prevent this, women will be asked to use a vaginal dilator with a lubricating jelly to keep the vaginal walls open and supple. Some women may also need to use lubricating jelly during sexual intercourse.

Infertility can also be a side effect of radiotherapy. If you are concerned about your risks of being infertile following treatment, it is a good idea to discuss this issue with your specialist before starting.


This is the use of anti-cancer (cytotoxic) drugs to destroy cancer cells. The chemotherapy drugs are usually given by injection into a vein (intravenously). They can temporarily reduce the number of normal cells in your blood. When your blood count is low you are more likely to get an infection and you may tire very easily. During chemotherapy your blood will be tested regularly and, if necessary, you may be given antibiotics to treat any infection. Blood transfusions may be given if you become anaemic due to chemotherapy.

Other side effects may include feeling sick (nausea) and vomiting.

Some chemotherapy drugs can also make your mouth sore and cause small mouth ulcers. Regular mouthwashes are important and your nurse will show you how to use these properly. If you don’t feel like eating meals, you can supplement your diet with nutritious drinks or soups. A wide range of drinks is available and you can buy them at most chemists. You can ask your doctor to refer you to a dietitian for advice about your diet.


Surgery may be used if initial treatment does not completely get rid of the cancer, or if there are signs that your cancer has returned. There are two main types of surgery: local resection and abdominoperineal resection.

Local resection  This may be used for small tumours on the outside of the anus. This operation only removes the area of the anus containing the cancer cells. The anal sphincter is not usually affected, and so normal bowel function is maintained for most people.

Abdominoperineal resection  This is the removal of the anus and rectum. This operation requires a permanent colostomy, which involves diverting the open end of the bowel on to the surface of the abdomen (tummy area), to allow faeces to be passed out of the body into a colostomy bag. The opening on the abdominal wall is known as a stoma.

CancerBACUP can send you information about having a colostomy. Although the idea of a colostomy is initially frightening and distressing for many people, most people find that they adapt over time and can return to normal activities. You will be able to get support and advice from the stoma nurse in your hospital.

Relieving symptoms following treatment

It is not unusual for people to find that they have distressing side effects for a time following treatment for anal cancer. Some people find that they have diarrhoea and occasional incontinence, as well as a feeling of bloatedness and wind. These symptoms are usually temporary but may last for up to several months.

It may help to discuss your symptoms with your doctor, nurse or a dietitian. They should be able to give you further advice about how to manage any problems.

Your feelings

During your diagnosis and treatment you are likely to experience a number of different emotions, from shock and disbelief to fear and anger. At times these emotions can be overwhelming and hard to control. It is quite natural, and important, to be able to express them. Everyone has their own ways of coping with difficult situations; some people find it helpful to talk to friends or family, while others prefer to seek help from people outside their situation. Others prefer to keep their feelings to themselves. There is no right or wrong way to cope, but help is available if you need it.


This section has been compiled using information from a number of reliable sources including;

  • Oxford Textbook of Oncology (2nd edition). Souhami et al. Oxford University Press, 2002.
  • Gastrointestinal Oncology: Principles and Practice. Kelsen et al. Lippincott Williams and Wilkins, 2002.
  • The Textbook of Uncommon Cancers (2nd edition). Raghavan et al. Wiley, 1999.

For further references, please see the general bibliography.