Anal Cancer

What is anal cancer?

Cancer describes a set of diseases in which normal cells in the body, through a series of genetic changes, lose the ability to control their growth and to respect their neighbours. As cancers grow, they invade the tissues around them (local invasion). They may also spread to other locations in the body via the blood vessels or lymphatic channels where they may implant and grow (metastases). Tumours, or growths in the body, may be benign or malignant (cancerous). When they are benign they may grow but they do not spread to other locations. Malignant tumours have the ability to invade deeply and to spread (metastasise).

Anal cancer arises from the cells around the anal opening (verge) or within the anal canal (1-2 inches long) up to its junction with the rectum. Most anal cancers arise from skin cells and are called squamous cell carcinomas. Some arise from the special mucosal cells lining the upper anal canal and are called cloacogenic carcinomas. Although several other types of cancer may occur in this area, these two are the most common. They behave similarly and are treated in the same fashion. Cells that are becoming malignant but have not invaded below the surface are “pre-cancerous” (carcinoma-in-situ). This condition is called Bowen’s disease.

How common is anal cancer?

Anal cancer is fairly uncommon. It accounts for about 1-2% of gastrointestinal cancers.

Who is at risk?

We do not know the exact cause of most anal cancers. But we do know that certain risk factors are linked to anal cancer. A risk factor is something that increases a person’s chance of getting a disease.

  • Age: Most people with anal cancer are over 50 years old.
  • Anal warts: Infection with the human papilloma virus (HPV) which causes condyloma (warts) may increase the chance of developing anal cancer.
  • Smoking: Harmful chemicals from smoking increase the risk of most cancers, including anal cancer.
  • Immunosuppression: People with weakened immune systems, such as transplant patients who must take drugs to suppress their immune systems and patients with HIV (human immunodeficiency virus) infection, are at a somewhat higher risk.
  • Chronic local inflammation: People with long-standing anal fistulas or open wounds are at a slightly higher risk.
  • Pelvic radiation: People who have had pelvic radiation therapy for rectal, prostate, bladder or cervical cancer are at an increased risk.

What are the symptoms of anal cancer?

Many cases of anal cancer can be found early. Anal cancers form in a part of the digestive tract that the doctor can see and reach easily. Anal cancers often cause symptoms such as:

  • Bleeding from the rectum or anus.
  • The feeling of a lump or mass at the anal opening.
  • Pain in the anal area.
  • Persistent or recurrent itching.
  • Change in bowel habits (having more or fewer bowel movements) or increased straining during a bowel movement.
  • Narrowing of the stools.
  • Discharge (mucous or pus) from the anus.
  • Swollen lymph nodes (glands) in the anal or groin areas.

These symptoms can also be caused by less serious conditions such as haemorrhoids, but you should never assume this. If you have any of these symptoms, see your doctor.

How is anal cancer diagnosed?

Finding cancers early is the key to cure. Regular checkups with a digital (finger) examination of the rectum and anus will find many problems which are easy to treat when found early. Routine screening for colorectal and anal cancer in people without any symptoms includes a digital rectal exam and test for blood in the stool yearly and a flexible endoscopy examination (lighted probe) every 5-10 years, starting at 50 years of age.

If anal cancer is suspected based on your doctor’s examination, a biopsy will be performed to confirm the diagnosis. If the diagnosis of cancer is confirmed, additional tests to determine the extent of the cancer may be recommended.

How are anal cancers treated?

Treatment for most cases of anal cancer is very effective. There are 3 basic types of treatment used for anal cancer:

  • Surgery – an operation to remove the cancer
  • Radiation Therapy – high-dose x-rays to kill cancer cells
  • Chemotherapy – giving drugs to kill cancer cells.


Combination therapy including radiation therapy and chemotherapy is now considered the standard treatment for most anal cancers. Occasionally a very small or early tumour may be removed surgically (local excision), with minimal damage to the anal sphincter muscles.

Will I need a colostomy?

The majority of patients treated for anal cancer will not need a colostomy,. If the tumour does not respond completely to combination therapy, if it recurs after treatment, or if it is an unusual type, an abdomino-perineal resection removal of the rectum and anus and creation of a colostomy may be necessary.

What happens after treatment for anal cancer?

Follow-up care to assess the results of treatment and to check for recurrence is very important. Most anal carcinomas are effectively treated. In addition, many tumours that recur may be successfully treated if they are caught early. A careful examination by an experienced physician at regular intervals is the most important method of follow-up. Additional studies may be recommended. You should report any symptoms or problems to your doctor immediately.


Anal cancers are unusual tumours arising from the skin or mucosa of the anal canal. As with most cancers, early detection is associated with excellent survival. Most tumours are well treated with combination chemotherapy and radiation. Recurrences may often be treated successfully. Follow the recommended screening examinations for anal and colorectal cancer and consult your doctor early when any anorectal symptoms occur.