Anal cancer

What is anal cancer?

Anal cancer is an uncontrolled growth of abnormal cells in the anus. The anus is the end of the large intestine, through which solid waste leaves the body. The treatments for anal cancer and rectal cancer can differ. Doctors need to know the exact location and the specific type of cell that has become cancerous in order to choose the right treatment.

The body stores digestive waste (feces) in the rectum, the lower part of the large intestine. The feces travel through the anal canal, a short tube that connects the rectum to the anal opening where they are passed as a bowel movement.

Several types of cells line the anal canal. Anal glands, which lie underneath the lining, lubricate the anal canal to ease bowel movements.

Several types of tumors can form in the anus. These include noncancerous tumors and cancerous tumors that can spread to other parts of the body. Some noncancerous growths can turn cancerous over time.

Risk factors of anal cancer

The strongest risk factor is infection with the human papillomavirus virus (HPV). HPV causes wart-like growths around the anus. The subtype HPV-16 has a particularly strong connection to anal cancer risk. However, most people with HPV do not develop anal cancer.

In general, other risk factors are similar to the risks of acquiring and/or not clearing an HPV infection:

• infection with the human immunodeficiency virus (HIV)
• prior history of cervical, vaginal or vulvar cancer
• multiple sexual partners
• anal intercourse
• frequent anal redness, swelling, and soreness
• abnormal anal openings (fistulas)
• weakened immune system
• prolonged use of steroid medicines, especially for patients who have had an organ transplant
• smoking.

Some people who develop anal cancer have no known risk factors.

Symptoms of anal cancer

• bleeding from the anus or rectum (can be minor)
• itching in the anal area
• pain in the anal area
• abnormal discharge from the anus
• change in size of bowel movements (stool may become more narrow)
• lump near the anus
• swollen lymph nodes in the anal/groin area.

Talk to your doctor if you experience any of these symptoms. Other conditions that are not cancer (such as hemorrhoids) may cause similar symptoms.

Diagnosing anal cancer

Sometimes doctors discover anal cancer during a routine physical exam or minor procedure. Some kinds of anal cancer may not cause symptoms until they're at an advanced stage. Your doctor may recommend the following tests to help diagnose anal cancer:

• Physical exam and medical history – The doctor will check for general signs of health or disease. He or she will ask about your health habits and past illnesses.
• Digital rectal exam – This is an exam of the anus and rectum. The doctor inserts a gloved, lubricated finger into the anus to feel for lumps or anything else that seems unusual.
• Endoscopy – For this test, the doctor uses a short lighted tube with an attached lens or video camera attached examine the anus, rectum, and part of the large intestine.
• Biopsy – This is surgery to remove a tissue sample that will be examined under a microscope to check for cancer. Sometimes the surgeon removes the entire tumor during the biopsy. A biopsy may also be used to detect whether cancer has spread to the lymph nodes.

If the tests show cancer, the next step is to see whether it has spread within the anus or to other parts of the body. This process is called staging. It is important for determining your treatment options.

Imaging tests may be done as part of the staging process. These may include:

• computed tomography (CT) scan or MRI of the pelvis, abdomen, and chest
• positron emission tomography (PET) scan.

Tumors of the anal canal are grouped into a set of stages. Stage 0 is the earliest stage, while stage IV is the most advanced. Sometimes anal cancer comes back after treatment. This is called recurrent anal cancer.

Expected duration of anal cancer

Without treatment, anal cancer will continue to grow.

Preventing anal cancer

To help reduce your risk of anal cancer:

• Practice safe sex. The best way to lower your risk of anal cancer is to avoid sexual behaviors that might expose you to HPV and HIV infections.
  • Use condoms to protect against sexually transmitted diseases.
  • Limit your number of sexual partners.
• Get the HPV vaccine.
• Don't smoke. Avoiding smoking can reduce your risk of developing anal cancer.

Treating anal cancer

There are several treatments for anal cancer. Your doctor will recommend specific therapies based on:

• the type of cancer cells — squamous cell cancer, adenocarcinoma, or perianal skin cancer
• the stage and location of the anal tumor
• whether the anal cancer has been previously treated.

The standard treatments are radiation, chemotherapy, and surgery, often in combination.

• Radiation therapy uses high-energy X-rays or other types of radiation to kill cancer cells and shrink tumors. The radiation can be delivered from a machine outside the body. Or it can come from a radioactive substance placed in or near the cancer cells.
• Chemotherapy uses drugs to kill cancer cells or stop them from dividing. Chemotherapy taken by mouth or injected into a vein or muscle travels through the bloodstream and body. This is called systemic chemotherapy. When placed into the spinal column, organ, or a body cavity such as the abdomen, chemotherapy affects mainly those areas. This is called regional chemotherapy.
• Surgery. Sometimes anal cancer is treated with surgery. The type of surgery depends on the size of the tumor and how far it has spread.
  • Local resection: This procedure involves removing the tumor from the anus. Some surrounding healthy tissue is removed as well. This procedure may be used if the cancer is small and has not spread. This surgery can save the muscles that control bowel movements.
  • Abdominoperineal resection: This procedure removes the anus, rectum, and part of the colon. Cancerous lymph nodes may be removed as well. The surgeon sews the end of the intestine to an opening made in the abdomen. This allows waste to empty into a bag (colostomy bag) outside the body.

The most effective therapies usually include both chemotherapy and radiation therapy.

When you talk to your doctor about the treatment options, ask him or her about the expected benefits and risks. How will this treatment affect your prognosis? What will your quality of life be during and after treatment?

Follow-up tests during treatment will show how well the therapy is working. You should continue to have regular follow-up tests after your treatment is over to show if your condition has changed.

When to call a professional

Call your doctor if you experience any of the symptoms of anal cancer, including:

• bleeding from the anus or rectum
• pain in the anal area
• abnormal discharge from the anus
• change in bowel movement size
• lump near the anus
• swollen lymph nodes in the anal/groin area.

Prognosis

Anal cancer is often curable with treatment. The person's outlook depends on the location and size of the tumor and whether the cancer has spread to the lymph nodes.

Additional info

National Cancer Institute (NCI)
https://www.cancer.gov/

American Cancer Society (ACS)
https://www.cancer.org/