Actress Farrah Fawcett had been battling anal cancer on and off for three years.

Program Note: For more on actress Farrah Fawcett and her battle with anal cancer, tune in tonight,  AC360° at 10 p.m. ET 

American Cancer Society &
National Cancer Institute

Anal cancer is fairly rare - much less common than cancer of the colon or rectum. The American Cancer Society estimates that in 2009 about 5,290 new cases of anal cancer will be diagnosed in the United States. The number of new anal cancer cases has been on the rise for many years.

Lifetime Risk
Based on rates from 2004-2006, 0.16% of men and women born today will be diagnosed with cancer of the anus, anal canal, and anorectum at some time during their lifetime. This number can also be expressed as 1 in 624 men and women will be diagnosed with cancer of the anus, anal canal, and anorectum during their lifetime. These statistics are called the lifetime risk. See Fast Stats for more detailed statistics, and Probability of Developing and Dying of Cancer for methodology.

What Are the Risk Factors for Anal Cancer?

• Human papillomavirus (HPV) infection: Most squamous cell anal cancers seem to be linked to infection by the human papilloma virus (HPV), the same virus thought to cause cervical cancer. There are several subtypes of the virus, but the one most likely to cause anal cancer is called HPV-16. This virus is most often spread by sexual contact and is more likely to be found in people who have had many sex partners. Different subtypes of HPV can cause genital warts (condylomas), but most people infected with HPV do not have genital warts.
• Sexual activity: Having multiple sex partners is a risk factor. Another risk factor is anal intercourse for both men and women, particularly younger than the age of 30.
• Smoking: Smoking also increases the risk of anal cancer. Current smokers are several times more likely to have cancer of the anus compared with people who do not smoke. Quitting smoking will reduce the risk. People who used to smoke but have quit are only slightly more likely to develop this cancer compared with people who never smoked.
• Lowered immunity/HIV infection: Higher rates of anal cancer occur among people with reduced immunity, such as people who have had an organ transplant and must take medicines that suppress their immune system. Another important risk factor is infection with the human immunodeficiency virus (HIV), the virus that causes AIDS. But effective drug treatment for HIV hasn't lowered the anal cancer rate in people infected with HIV.

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