Anal Cancer
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Anal Cancer

En Español (Spanish Version)

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

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© 2008 Nucleus Medical Art, Inc.

Causes

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

Risk Factors

A risk factor is something that increases your chance of getting a disease or condition.

Some people with this condition have no known risk factors, but the following factors increase your chance of developing anal cancer. If you have any of these risk factors, tell your doctor:

Symptoms

Some anal cancers do not have symptoms. If you do experience symptoms do not assume it is because of anal cancer. These symptoms may be caused by other, less serious health conditions. If you experience any one of them, see your physician.

  • 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

Diagnosis

Your doctor will ask about your symptoms and medical history, and perform 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
  • Chest x-ray
  • CT scans of the abdomen and pelvis
  • Positron emission tomography scan (PET)
  • Laboratory tests, with particular attention paid to 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 can be given in the form of pills, injections, and via a catheter. 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. In some cases, radiation therapy alone may be used if chemotherapy is thought to result in too many side effects (ie, 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.

Combined Chemoradiation Therapy

Combined chemoradiation therapy has had a high rate of local control and survival (82%) when compared to surgery.

Surgery

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

Prevention

There are no known ways of avoiding anal cancer, though potentially reducing exposure to HPV and HIV may reduce the likelihood of developing this cancer.

In addition, researchers are investigating whether vaccines designed to prevent HPV infection and reduce the risk of cervical cancer could also prevent other HPV-related cancers, including anal cancer.

A study published in Lancet (2007) found that the HPV vaccine was related to a significant reduction in the likelihood of premalignant lesions of the vulva, cervix, and anus which were thought to be linked to HPV infection. Vaccinations to reduce HPV and, as such, reduce the development of anal cancer, are still considered investigational.

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:

Cancer of anus canal. DynaMed website. Available at: http://dynamed102.epnet.com/Detail.aspx?style=1&docid=/dynamed/2b3a2a4fac3be499852562b60006d7be. Accessed April 19, 2007.

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.

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 April 2008 by Rimas Lukas, MD

Please be aware that this information is provided to supplement the care provided by your physician. It is neither intended nor implied to be a substitute for professional medical advice. CALL YOUR HEALTHCARE PROVIDER IMMEDIATELY IF YOU THINK YOU MAY HAVE A MEDICAL EMERGENCY. Always seek the advice of your physician or other qualified health provider prior to starting any new treatment or with any questions you may have regarding a medical condition.

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