What is anal cancer?Anal cancer is cancer found in the anus. The anus is the opening through which body waste passes. The anus is the opening at the end of the rectum (the end part of the large intestine) through which body waste passes. Cancer of the anus (anal cancer) is very rare, and is the result of abnormal cell growth in the anus. Cancer of the outer part of the anus is more
likely to occur in men, while cancer of the inner part of the rectum occurs more often in women.
Anal cancer, an uncommon cancer, is a disease in which cancer cells develop in the anus. Cancer may develop inside the body in the tissues of the anal canal or in the anal sphincter or the outside area of the anus. Cancer in the outer part of the anus is more likely to occur in men, while cancer that forms inside the anal canal is more likely to occur in women. Tumors found in the area of skin with hair on it just outside the anus are skin tumors, not anal cancer.
Different cancers can develop in different parts of the anus, part of which is inside the body and part of which is outside. Sometimes abnormal changes of the anus are harmless in their early stages but may later develop into cancer. Some anal warts, for example, contain precancerous areas and can develop into cancer. Approximately half of anal cancers are squamous cell carcinomas, which arise from the cells lining the anal margin and the anal canal. The anal margin is the part of the anus that is half inside and half outside the body, and the anal canal is the part of the anus that is inside the body. The earliest form of squamous cell carcinoma is known as carcinoma in situ, or Bowen's disease. Approximately one-fourth to one-third of anal tumors are cloacogenic carcinomas. These tumors develop in the transitional zone, or cloaca, which is a ring of tissue between the anal canal and the rectum. About 15% of anal cancers are adenocarcinomas, which affect glands in the anal area. One type of adenocarcinoma that can occur in the anal area is called Paget's disease, which can also affect the vulva, breasts, and other areas of the body. A small percentage of anal cancers are either basal cell carcinomas, or malignant melanomas, two types of skin cancer. Malignant melanomas, which develop from skin cells that produce the brown pigment called melanin, are far more common on areas of the body exposed to the sun.
What causes anal cancer?The exact cause of most anal cancers is unknown, although certain individuals appear to have a higher risk of developing the disease. Smokers are at higher risk, as are individuals with certain types of the human papillomavirus (HPV), and those with long-term problems in the anal area, such as abnormal openings known as fistulas. Since it increases the risk of HPV infection, the practice of anal sex appears to increase the risk of anal cancer-male homosexuals who practice anal sex are about 33 times more likely to have anal cancers than heterosexual men. Those with weakened immune systems, such individuals with HIV, or transplant patients taking immunosuppressant drugs, are also at higher risk. Most individuals with anal cancer are over the age of 50. It is known that anal cancer is 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.
What are the risk factors for cancer?The risk factors for developing anal cancer include the following:
- Anal intercourse: The human pillomavirus (HPV) can cause anal warts, which sometimes causes cancer. HPV can be transmitted through anal intercourse, and cannot be prevented by using condoms.
- Smoking: Smokers are eight times more likely than nonsmokers to develop anal cancer. Smokers can reduce their risk by quitting.
- Weakened immune systems: People with weakened immune systems, such as transplant patients or people with various types of chronic illnesses, are at a higher risk for developing anal cancer.
- Age: Anal cancer is most common in people over the age of 50 and highest in people over age 85.
- Other medical conditions:People with chronic problems in the anal area and people with lowered immune system function have an increased risk of developing anal cancer.
What are the symptoms of anal cancer?Symptoms of anal cancer resemble those found in other harmless conditions. They include pain, itching and bleeding, straining during a bowel movement, change in bowel habits, change in the diameter of the stool, discharge from the anus, and swollen lymph nodes in the anal or groin area. People with anal cancer often experience bleeding with bowel movements, pain, and sometimes itching around the anus. About 25% of people with anal cancer have no symptoms; in these instances, the cancer is found only during a routine examination.
How is anal cancer diagnosed?Anal cancer is sometimes diagnosed during routine physicals, or during minor procedures such as hemorrhoid removal. It may also be diagnosed during a digital rectal examination (DRE), when a physician inserts a gloved, lubricated finger into the anus to feel for unusual growths. Individuals over the age of 50 who have no symptoms should have a digital rectal examination (DRE) every five to 10 years, according to American Cancer Society (ACS) guidelines for early detection of colorectal cancer.
Other diagnostic procedures for anal cancer include: Anoscopy. A procedure that involves use of a special device to examine the anus. Proctoscopy. A procedure that involves use of a lighted scope to see the anal canal. Transrectal ultrasound. A procedure in which sound waves are used to create an image of the anus and nearby tissues.
A biopsy is performed on any suspicious growths; that is, a tiny piece of the growth is examined under a microscope for cancer cells. The physician may also perform a procedure called a fine needle aspiration biopsy, in which a needle is used to withdraw fluid from lymph nodes located near the growth, to make sure the cancer hasn't spread to these nodes.
What're the stages of anal cancer?Stage 0: The cancer is found only in the top layer of anal tissue. During this stage, treatment will probably be simple surgery to remove all of the cancer.
Stage I: The cancer has spread beyond the top layer of anal tissue, is smaller than two centimeters in diameter (less than one inch), and has not spread to the muscle tissue of the sphincter.
Stage IIIA: The cancer has spread to the lymph nodes around the rectum or to nearby organs such as the vagina or bladder.
Stage IIIB: The cancer has spread to the lymph nodes in the middle of the abdomen or in the groin, or the cancer has spread to both nearby organs and the lymph nodes around the rectum.
Stage IV: The cancer has spread to distant lymph nodes within the abdomen or to organs in other parts of the body.
Recurrent: Recurrent cancer is cancer that has come back (recurred) after it has been treated. It may come back in the anus or in another part of the body.
What're the treatments for anal cancer?Anal cancer is treated using three methods, used either in concert or individually: surgery, radiation therapy, and chemotherapy.
Two types of surgery may be performed. A local resection, performed if the cancer has not spread, removes the tumor and an area of tissue around the tumor. 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 muscle that opens and closes the anus to allow the faeces to be passed normally is not usually affected, and so normal bowel function is maintained for most people. An abdominoperineal resection is a more complex procedure in which the anus and the lower rectum are removed, and an opening called a colostomy is created for body wastes to exit. This procedure is fairly uncommon today because radiation and chemotherapy are just as effective. 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.
Radiation therapy uses high-energy rays to fight cancer cells. It is usually delivered via a machine outside the body, but may also be delivered via surgically implanted radioactive pellets. This latter method is called internal radiation, brachytherapy, or interstitial radiation. Side effects of radiation may include tiredness, skin damage resembling sunburn, and damage to anal tissues. 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 advice.
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.
Chemotherapy fights cancer using drugs, which may be delivered via pill or needle. Some chemotherapy types kill cancer cells directly, while others act indirectly by making cancer cells more vulnerable to radiation. The main drugs used to treat anal cancer are 5-fluorouracil (5-FU) and mitomycin or 5-FU and cisplatin. Side effects of chemotherapy, which damages normal cells in addition to cancer cells, may include nausea and vomiting, hair loss, loss of appetite, diarrhea, mouth sores, fatigue, shortness of breath, and a weakened immune system. 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.