Risk factors

Several factors have been found to increase the risk of anal cancer, including:

• Older age. Most cases of anal cancer occur in people age 50 and older.
• Many sexual partners. People who have many sexual partners over their lifetimes have a greater risk of anal cancer.
• Anal sex. People who engage in receptive anal sex have an increased risk of anal cancer.
• Smoking. Smoking cigarettes may increase your risk of anal cancer.
• History of cancer. Those who have had cervical, vulvar or vaginal cancer have an increased risk of anal cancer.
• Human papillomavirus (HPV). HPV infection increases your risk of several cancers, including anal cancer and cervical cancer. HPV infection is a sexually transmitted infection that can also cause genital warts.
• Drugs or conditions that suppress your immune system. People who take drugs to suppress their immune systems (immunosuppressive drugs), including people who have received organ transplants, may have an increased risk of anal cancer. HIV — the virus that causes AIDS — suppresses the immune system and increases the risk of anal cancer.