A risk factor is anything that may increase your risk for a disease. Risk factors for anal cancer include:
- Being older than 50
- Infection with human papillomavirus (HPV)
- Infection with human immunodeficiency virus (HIV), the virus that causes AIDS
- Lowered immunity, often from taking immune-suppressing drugs to prevent organ rejection after a transplant
- Having multiple sexual partners
- Having anal fistulas or abnormal openings
Infection with Human Papillomavirus
There is a strong link between anal cancer and infection with HPV. HPV is a collection of more than 150 related viruses, and about 40 of them may be spread through sexual contact. Most of these viruses are harmless, pose no symptoms and the infection clears without treatment. However, certain HPV infections persist, and are known to cause genital warts and/or cancers of the cervix, anus and genital areas.
The strains known as HPV-6 and HPV-11 cause 90 percent of genital warts, and HPV-16 and HPV-18 cause about 70 percent of cancer cases involving the cervix and anus. Currently, two HPV vaccines are available to prevent these viruses. One protects against HPV-16 and 18; the other protects against all four. The federal Advisory Committee on Immunization Practices (ACIP) recommends that girls and women age 9 to 25 receive the 3-dose immunization, as well as boys and men age 11 to 21 to prevent HPV infection.