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In anal cancer, malignant (i.e. cancer cells that can spread) form in the tissues of the anus. The anus, which is the opening of the rectum (last part of the large intestine) to the outside of the body, is formed partly from the outer layers skin, and partly from the intestine. The ring-like sphincter muscles open and close the anal opening to allow faeces to pass out of the body.
Anal cancer starts in the cells lining the anus. From there it can spread to nearby organs, such as the vagina, urethra or bladder. The malignant cells can also enter the lymphatic system, and be carried to more distant organs where they may develop into tumours.
Anal cancer is much rarer than cancer of the rectum or large intestine (colon).
What causes anal cancer?
The exact causes of anal cancer are still not well understood, but there are certain risk factors that increase the risk.
The likelihood you will develop this kind of cancer increases if you:
- Are over 50
- Are infected with human papillomavirus (HPV), the same virus that causes cervical cancer. According to the American Cancer Society, 85% of anal cancers are associated with persistent HPV infection.
- Have had many sexual partners
- Have had receptive anal sex (i.e you are penetrated by your partner during intercourse)
- Experience frequent anal redness, swelling and soreness.
- Have anal fistulas (abnormal openings around the anus)
- Smoke
Symptoms of anal cancer
The following may be symptoms of anal cancer (as well as several other conditions):
- Bleeding from the anus.
- Pain or pressure in the area around the anus.
- Itching or discharge from the anus.
- A lump near the anus.
- A change in bowel habits.
It's very important to consult your doctor without delay if you notice any of the above symptoms; if they do indicate cancer, the sooner it is diagnosed and treated, the better the outcome will be.
Can anal cancer be treated?
Treatment for anal cancer depends on how far the cancer has spread. If it is caught in its earliest stages, 82% of patients will live for five years or more after diagnosis. If the cancer has spread to surrounding lymph nodes, five-year survival is 60%. When it has spread to distant organs, five-year survival is only about 20%.
In the earlier stages, treatment may involve surgery to remove the tumour and some of the healthy tissue surrounding it, in case this contains malignant cells. If the tumour is small enough and situated low down the near the anal opening, then it may be possible to save the sphincter muscles, and the patient will still be able to control their bowel movements.
In other cases, however, the anus, rectum and part of the colon (large intestine) may need to be removed. The surgeon then sews the end of the intestine to an opening made in the surface of the abdomen so that waste can be collected in a disposable bag (colostomy bag) outside the body.
If the cancer has spread, treatment may involve radiation therapy or chemotherapy. Sometimes a combination of treatment therapies are required.
(- Health24, June 2009)
Adapted from General Information about anal cancer, National Institutes of Health, National Cancer Institute. 2009.
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