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Anal Cancer Primer

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In late 2010 the FDA green-lighted use of Merck’s Gardasil® vaccine for the prevention of anal cancers in males and females ages 9-26. The new indication put a spotlight on a disease that had already gathered more attention following Farrah Fawcett’s death from anal cancer in 2009.

What is anal cancer?
Most anal cancers are squamous cell carcinomas that develop in the anal canal (the passage linking the lower intestine to the outside of our bodies). Squamous cells are tough, flat cells that are part of the epidermis (the top most layer of skin).

The American Cancer Society (ACS) estimates there about 5,200 new cases (with approximately 700 deaths) each year in the U.S. Women are affected more than men, although men who have sex with men (MSM) are at high risk for anal cancers.

Signs and Symptoms:

  • Bleeding, itching, discharge, or pain with the anus or rectum (symptoms can mimic those found with hemorrhoids)
  • Lumps or bumps in the anus
  • Swollen glands in the groin or anus
  • Change in stools or bowl movements (going more or less often)
  • Not all cases involve symptoms, or symptoms might be minor

What are risk factors for anal cancer?

  • Infection with high-risk HPV types
  • Having a weakened immune system (for example, being HIV positive or a transplant patient)
  • Anal sex
  • A history of having cervical or vaginal cancer
  • Smoking

What is the link between HPV and anal cancer?
As with cervical cancer, high-risk types of HPV are found in most anal cancers. HPV produces proteins that are able to ‘turn off” other proteins that the immune system uses to suppress and clear tumor cells. Hampering the immune response in this way is a key part in allowing cells to become abnormal and progress along to cancer.

Transmission of HPV to the anal canal is usually (but not always) by anal sex. Since HPV is acquired through skin-to-skin contact with an area that contains the virus, penetration is not necessary for transmission to occur. But fingers and sex toys are also possible routes of introducing HPV to the anus, especially when HPV-related lesions are present in the genital or perianal area. Females and gay men are not the only ones at risk: It’s not uncommon for anal HPV to be detected in men who report no history of sexual contact with other men, and in women who have never had anal intercourse.

Screening tests
Anal cytology (Pap tests): Anal Pap tests involve taking cell samples from the anal canal which are then viewed under microscope and examined for abnormalities. Much like cervical cytology, anal Paps seek to detect abnormal cell changes or lesions of the epithelium (surface of the skin), ideally before cancer develops. Precancerous anal lesions are referred to as anal intraepithelial neoplasia (AIN) or anal squamous intraepithelial lesion (ASIL). Depending on their severity, size, and risk to progress to cancer, lesions can be classified as either low-grade or high-grade.

Follow-up for patients with abnormal cell changes detected is high resolution anoscopy (HRA). A procedure similar to cervical colposcopy, HRA uses a special microscope to examine the anal area. Any suspicious lesions detected are biopsied.

Treatment
Low-grade lesions are often monitored, while high-grade lesions may either be monitored or treated. Treatment for anal cancer includes:

  • Surgery
  • Radiation therapy
  • Chemotherapy
  • Combination therapy (radiation and chemotherapy used in tandem)


Prevention

  • One HPV vaccine, Gardasil®, is approved for the prevention of anal cancers in males and females ages 9-26.
  • Practice safer sex such as using condoms. Condoms aren’t 100% effective at preventing HPV transmission, but using them consistently and correctly can reduce the risk of acquiring the virus.
  • Stop smoking.
  • Anal Pap tests for those with risk factors for anal cancer (see What are risk factors for anal cancer above).

Sources
American Society of Colon & Rectal Surgeons: Anal Cancer
American Cancer Society: Detailed Guide to Anal Cancer
Richard Ortoski, DO and Christine Kell, PhD. Anal Cancer and Screening Guidelines for Human Papillomavirus in Men. Journal of the American Osteopathic Association, March 2011.
111(S2), 3, S35-S43.
UCSF AIDS Research Institute. Anal Cancer In Gay and Bisexual Men