Anal cancer is a rare form of cancer that occurs in the anus. The anus is a 1 1/2-inch tube at the end of your rectum through which stool leaves your body. Muscles called sphincters surround the anus and control bowel movements.

About 4,600 people are diagnosed with anal cancer annually, according to the American Cancer Society. While anal cancer is rare, its incidence appears to be increasing, though it isn't completely clear why.

Treatment for anal cancer in the past typically meant extensive surgery and the removal of the anus. Today doctors have found ways to control anal cancer through radiation and chemotherapy, saving the anus and preserving normal bowel function for anal cancer survivors. But that isn't always possible for late-stage anal cancers. However, the majority of anal cancer is caught in its earliest stages — when treatment provides the best chance for cure.

Anal cancer signs and symptoms include:

• Bleeding from the anus or rectum
• Pain in the area of the anus
• A mass or growth in the anus
• Anal itching
• Anal discharge
• A feeling of fullness in the anal area

Some people don't experience any anal cancer signs and symptoms.

In general, cancer begins with a genetic mutation that turns normal, healthy cells into abnormal cells. Healthy cells grow and multiply at a set rate, eventually dying at a set time. Abnormal cells grow and multiply out of control, and they don't die. The accumulating abnormal cells form a mass (tumor). Cancer cells invade nearby tissues and can separate from an initial tumor to spread elsewhere in the body (metastasize).

Doctors don't know what causes the genetic mutation that triggers the development of anal cancer. However, they have identified several factors that may increase the risk of anal cancer.

Several factors have been found to increase the risk of anal cancer, including:

• Your sex. Women have a higher risk of anal cancer than do men.
• Your age. Most cases of anal cancer occur in people age 50 and older.
• Having many sexual partners. Men and women who have many sexual partners over their lifetimes have a greater risk of anal cancer.
• Anal sex. Men and women who engage in anal sex have an increased risk of anal cancer.
• Smoking. Smoking cigarettes may increase your risk of anal cancer. Former smokers have only a slightly elevated risk of anal cancer.
• Human papillomavirus (HPV). HPV infection increases your risk of several cancers, including anal cancer and cervical cancer. HPV is a sexually transmitted disease that can also cause genital warts. HPV may cause cells in the anus to appear abnormal — a condition called anal squamous intraepithelial lesions (ASIL). The abnormal cells associated with ASIL aren't cancer, but they may develop into anal cancer. However, some people with ASIL never develop anal cancer.
• Drugs or conditions that suppress your immune system. People who take drugs to suppress their immune systems (immunosuppressive drugs), including people who have received organ transplants, may have an increased risk of anal cancer. Long-term use of corticosteroids, such as those prescribed to control autoimmune disorders, also may increase the risk of anal cancer. HIV — the virus that causes AIDS — suppresses the immune system and increases the risk of anal cancer.

The signs and symptoms of anal cancer aren't specific to this disease. Some people mistake their signs and symptoms for more common conditions, such as hemorrhoids, and don't see their doctors. Talk to your doctor about any signs and symptoms that bother you, especially if you have any factors that increase your risk of anal cancer. Treatment for anal cancer is more likely to succeed if cancer is found at an earlier stage.

Tests and procedures used to diagnose anal cancer include:

• Feeling your anus and rectum for abnormalities. During a digital rectal exam (DRE), your doctor inserts a gloved, lubricated finger into your rectum. He or she feels for anything unusual, such as growths. DRE isn't used to diagnose anal cancer, but it can give your doctor an indication of what further testing might be appropriate.
• Visually inspecting your anus and rectum. Your doctor may use a short lighted tube (anoscope) to inspect your anus and rectum for anything unusual. Your doctor inserts the lubricated tube into your rectum to examine your anus, anal canal and rectum. You may feel pressure during anoscopy, but it shouldn't hurt. You may be required to take laxatives or an enema in order to clean your rectum before the procedure.
• Taking sound wave pictures of your anus. In order to create a sonogram picture of your anus, your doctor inserts a probe, similar to a thick thermometer, into your anus and rectum. The probe emits high-energy sound waves, called ultrasound waves, which bounce off tissues and organs in your body to create a picture. Your doctor evaluates the sonogram picture to look for anything abnormal.
• Removing a sample of tissue for laboratory testing. If your doctor discovers any unusual areas, he or she may take small samples of affected tissue (biopsy) and send the samples to a laboratory for analysis. By looking at the cells under a microscope, doctors can determine if the cells are cancerous. Biopsy samples are typically removed during anoscopy. You may feel a pinch and experience some bleeding during a biopsy procedure.

Staging
Once your doctor confirms that you have anal cancer, he or she works to determine the size of the cancer and whether it has spread — a process called staging. Determining your cancer's stage helps your doctor determine the best way to treat your cancer. Tests and procedures used in the staging of your cancer may include:

• Images of your pelvis and abdomen. Your doctor may use computerized tomography (CT) scans of your pelvis and abdomen to assess the extent of your cancer in that area.
• X-ray images of your chest. X-rays of your chest can reveal if cancer has spread to your lungs or the bones in your chest.

Your doctor uses the information from the procedures to assign your cancer a stage. The stages of anal cancer are:

• Stage I. Anal cancer is 2 centimeters or less — about the size of a peanut or smaller.
• Stage II. Anal cancer is larger than 2 centimeters, but has not spread beyond the anus.
• Stage IIIA. Anal cancer is any size and has spread to lymph nodes near the rectum or it has spread to nearby areas, such as the bladder, urethra or vagina.
• Stage IIIB. Anal cancer is any size and has spread to nearby areas and lymph nodes, or it has spread to lymph nodes in the pelvis.
• Stage IV. Anal cancer has spread to parts of the body away from the pelvis.

Anal cancer rarely spreads (metastasizes) to distant parts of the body. Only a small percentage of tumors are found to have spread, but those that do are especially difficult to treat. Anal cancer that metastasizes most commonly spreads to the liver and the lungs.

What treatment you receive for anal cancer depends on the stage of your cancer. Treatment most commonly involves chemotherapy and radiation, though sometimes surgery also is used. In the past, doctors usually treated anal cancer with extensive surgery. Today doctors try other methods first in an attempt to preserve bowel function for people with anal cancer.

Combined chemotherapy and radiation
Doctors treat anal cancer with a combination of chemotherapy and radiation. Combined, these two treatments enhance each other and improve chances for a cure.

• Chemotherapy. Chemotherapy drugs are injected into a vein or taken as pills. The chemicals travel throughout your body, killing rapidly growing cells, such as cancer cells. Unfortunately they also damage healthy cells that grow rapidly, including those in your gastrointestinal tract and in your hair follicles. This causes side effects such as nausea, vomiting and hair loss. Doctors commonly use a chemotherapy drug called 5-fluorouracil (Adrucil), which is sometimes referred to as 5-FU, to treat anal cancer. Your doctor may combine 5-FU with another chemotherapy drug called mitomycin (Mutamycin).
• Radiation therapy. Radiation therapy uses high-powered beams, such as X-rays, to kill cancer cells. During radiation therapy, you're positioned on a table and a large machine moves around you, directing radiation beams to specific areas of your body in order to target your cancer. Radiation may damage healthy tissue near where the beams are aimed. Side effects may include skin redness and sores in and around your anus, as well as hardening and shrinking of your anus.

You typically undergo radiation therapy for five or six weeks. Chemotherapy is typically administered during the first week and the fifth week. Your doctor tailors your treatment schedule based on characteristics of your cancer and your overall health. Though combining chemotherapy and radiation increases the effectiveness of the two treatments, it also makes side effects more likely. Discuss with your doctor what side effects to expect.

People with HIV are more likely to experience side effects when undergoing chemotherapy and radiation, since treatments can weaken their already-vulnerable immune systems. Side effects make it more difficult to endure and complete treatment. For this reason, your doctor may recommend lower doses of chemotherapy and radiation if you have HIV.

Surgery
Doctors typically use two different procedures to remove anal cancer based on your stage of cancer:

• Surgery to remove early-stage anal cancers. Very small anal cancers that haven't spread beyond the anus may be removed through surgery. During this procedure, the surgeon removes the tumor and a small amount of healthy tissue that surrounds it. Because the tumors are small, early-stage cancers can sometimes be removed without damaging the anal sphincter muscles that surround the anus. Anal sphincter muscles control bowel movements, so doctors work to keep the muscles intact. Depending on your cancer, your doctor may also recommend chemotherapy and radiation after surgery.

  If your cancer can't be removed without damaging the anal sphincters, your doctor may recommend trying combined chemotherapy and radiation first. Combined treatment may shrink your cancer to a size that allows your surgeon to perform sphincter-sparing surgery.

• Surgery for late-stage anal cancers or anal cancers that haven't responded to other treatments. If your cancer hasn't responded to chemotherapy and radiation, or if your cancer is advanced, your doctor may recommend a more extensive operation called abdominoperineal resection, which is sometimes referred to as an AP resection. During this procedure the surgeon removes the anus, rectum and a portion of the colon. The surgeon then attaches the remaining portion of your colon to an opening in your abdomen (stoma) through which waste will leave your body and collect in a colostomy bag.

No sure way to prevent anal cancer exists. In order to reduce your risk of anal cancer:

• Practice safe sex. Abstaining from sex or practicing safe sex may help prevent HPV and HIV, two sexually transmitted viruses that may increase your risk of anal cancer. If you choose to have anal sex, use condoms.
• Get vaccinated against HPV. The Food and Drug Administration approved a vaccine against HPV in early 2006. The HPV vaccine is approved only for girls and women. Doctors hope the vaccine will help prevent HPV-related cancers in women, including cervical cancer and anal cancer. Further study may reveal that the vaccine may also be appropriate for boys and men, though they currently can't receive the vaccine because it isn't approved for males.
• Stop smoking. Smoking increases your risk of anal cancer. Don't start smoking. Quit if you currently smoke.

A cancer diagnosis can be overwhelming and frightening. You can help yourself to feel more in control of your cancer and your emotions by taking an active role in your health care. To help you cope, try to:

• Learn everything you can about anal cancer. Write down all the questions that are going through your mind and ask them at the next appointment with your doctor. Have a friend or family member come to appointments with you to take notes. Ask your health care team for further sources of information. The more you know about your condition, the better prepared you'll be to make decisions about your treatment. Contact the National Cancer Institute for information online or by telephone at 800-4-CANCER, or 800-422-6237. The American Cancer Society also offers support and information on its Web site and by telephone at 800-ACS-2345, or 800-227-2345.
• Create a support network. Having friends and family around you and supporting you can be valuable. You may find it helps to have someone to talk to about your emotions. Other people who may provide support include social workers and psychologists — ask your doctor for a referral if you feel the need to talk to someone. Talk with your pastor, rabbi or other spiritual leader. Other people with cancer can offer a unique perspective, so consider joining a support group — whether it's in your community or online. Contact the American Cancer Society for more information on support groups.
• Take time for yourself when you need it. Let people know when you want to be alone. Quiet time to think or write in a journal can help you sort out your emotions.
• Take care of yourself. Prepare yourself for treatment by making healthy lifestyle choices. For instance, if you smoke, quit smoking. Eat a variety of fruits and vegetables. Get exercise when you feel up to it, but check with your doctor before starting a new exercise program. Try to get enough sleep so that you wake feeling refreshed. Talk to your doctor if you're having trouble sleeping. Try to control stress by prioritizing what's important to you. These healthy choices make it easier for your body to cope with the side effects of treatment.