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Anal Cancer by Krisha McCoy, MS

Definition

Anal cancer is cancer of the anus. This is the canal at the end of the large intestine, below the rectum.

Cancer occurs when cells in the body (in this case the cells that cover the lumen of the anus) divide without control or order. Normally, cells divide in a regulated manner. If cells keep dividing uncontrollably when new cells are not needed, a mass of tissue forms, called a growth or tumor. The term cancer refers to malignant tumors, which can invade nearby tissues and spread to other parts of the body. A benign tumor does not invade or spread.

The Anus

Causes

The exact cause of anal cancer is not clearly understood. But, there is evidence that human papillomavirus (HPV) causes many anal cancers.

Risk Factors

Risk factors include:

Having receptive anal intercourse
Having multiple sexual partners
Having HPV infection
Having HIV infection
Receiving immunosuppressant drugs
Being over 50 years old
Smoking
Having cervical dysplasia or cervical cancer
Low CD4 count (cells that are part of the immune system)

Symptoms

If you have any of these symptoms, do not assume it is due to anal cancer. These symptoms may be caused by other conditions. Tell your doctor if you have any of these:

Anal bleeding
Pain or pressure around the anus
Itching or discharge from the anus
A lump near the anus
Change in bowel habits (thinning in the width of the stool)
Bleeding both with and without a bowel movement

Some anal cancers do not have symptoms.

Diagnosis

Your doctor will ask about your symptoms and medical history. He will also do a physical exam. Tests may include the following:

Digital rectal examination
Anoscopy—exam of the anus and lower rectum
Proctoscopy—exam of the rectum
Transrectal ultrasound—a probe is inserted into the anus and/or rectum so your doctor can view the internal tissues
Biopsy —the removal of cells to test for cancer in a laboratory
X-ray —a test that uses radiation to take a picture of structures inside the body
CT scan —a type of x-ray that uses a computer to make pictures of structures inside the abdomen and pelvis
PET scan —a test that makes images to show activity in body tissue
Combined CT and PET scan
MRI scan —a test that uses magnetic waves to make pictures of structures inside the body
Lab tests—focusing on the function of the bone marrow, kidneys, and liver

Treatment

Talk with your doctor about the best treatment plan for you. Treatment options include the following:

Chemotherapy

In chemotherapy , drugs are used to kill cancer cells. Chemotherapy drugs travel through the bloodstream throughout the body to kill mostly cancer cells, but also some healthy cells. In the management of anal cancer, chemotherapy is given by vein, usually every three weeks during the course of daily radiation therapy.

Radiation Therapy

Radiation therapy is often delivered at the same time as chemotherapy. Compared to surgery, a combination of chemotherapy and radiation therapy can increase the survival rate.

In some cases, radiation therapy alone may be used if chemotherapy is thought to result in too many side effects (eg, in patients with HIV). In the treatment of anal cancer, radiation is delivered externally on a daily basis over 5-6 weeks.

Since radiation therapy damages healthy tissue as well as cancer cells, there are certain side effects associated with radiation therapy for the treatment of anal cancer. Scar tissue may form in the anus, keeping the anal sphincter from working properly. In addition, damage may occur that results in chronic rectal bleeding.

Surgery

Because of the location of the anus, an invasive cancer requires an abdominoperineal resection (APR). This surgery results in the formation of a permanent colostomy or bag. It is only considered if the cancer comes back after chemotherapy and radiation, or if radiation cannot be done for some reason.

Prevention

There are no known ways of avoiding anal cancer. You may be able to reduce your risk of anal cancer, though, by reducing your exposure to HIV and HPV. There is a vaccine available, called Gardasil, that protects against four types of HPV.

RESOURCES:

American Cancer Society http://www.cancer.org/
National Cancer Institute http://www.cancer.gov/

CANADIAN RESOURCES:

Canadian Cancer Society http://www.cancer.ca/
National Cancer Institute of Canada http://www.ncic.cancer.ca/

References:

Casciato DA. Manual of Clinical Oncology . 5th ed. Philadelphia, PA: Lippincott Williams & Wilkins; 2004.
Detailed guide: anal cancer. American Cancer Society website. Available at: http://www.cancer.org/docroot/CRI/CRI_2_3x.asp?rnav=cridg&dt=47 . Accessed April 19, 2007.
DynaMed Editorial Team. Cancer of anus canal. EBSCO DynaMed website. Available at: http://www.ebscohost.com/dynamed/what.php . Accessed April 19, 2007.
General information about anal cancer. National Cancer Institute website. Available at: http://www.cancer.gov/cancerinfo/pdq/treatment/anal/patient . Accessed April 19, 2007.
Joura EA, Leodolter S, Hernandez-Avila M, et al. Efficacy of a quadrivalent prophylactic human papillomavirus (types 6, 11, 16, and 18) L1 virus-like-particle vaccine against high-grade vulval and vaginal lesions: a combined analysis of three randomised clinical trials. Lancet . 2007; 369:1693.
Uronis HE, Bendell JC. Anal cancer: an overview. Oncologist . 2007;12:524-534.

Last reviewed December 2011 by Mohei Abouzied, MD

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