Risk factors for anal cancer
A risk factor is something that increases the risk of developing cancer. It could be a behaviour, substance or condition. Most cancers are the result of many risk factors. Human papillomavirus (HPV) infection is the most important risk factor for anal cancer.
The risk of developing anal cancer increases with age. It is usually seen in people over the age of 55. In general, anal cancer develops more often in women than in men. But Black men (including men of African or Caribbean ancestry) have a higher rate of anal cancer than white men or Black women.
Precancerous conditions of the anus include anal intraepithelial neoplasia (AIN). AIN isn’t cancer, but it can sometimes become anal cancer if it isn’t treated. Some of the risk factors for anal cancer may also cause this precancerous condition. Find out more about precancerous conditions of the anus.
Risk factors are generally listed in order from most to least important. But in most cases, it is impossible to rank them with absolute certainty.
Risk factors @(Model.HeadingTag)>
Human papillomavirus (HPV) infection
History of cervical, vaginal or vulvar cancer
There is convincing evidence that the following factors increase your risk for anal cancer.
Human papillomavirus (HPV) infection @(Model.HeadingTag)>
HPV infection is found in about 90% of people with anal cancer. There are several subtypes of the virus, but HPV16 and HPV18 are most likely to cause anal cancer. HPV infection can also cause cervical, vaginal, vulvar, penile and some oral cavity and oropharyngeal cancers.
Infection with HPV is common. In most cases, a person’s healthy immune system will clear the infection on its own. But in some cases, the infection does not go away and can eventually cause certain cancers, including anal cancer.
HPV is easily passed from one person to another through skin-to-skin sexual contact with an area of the body infected with HPV. A person can become infected with HPV without having sexual intercourse. An HPV infection can spread from one part of the body to another. For example, the infection may start in the genitals and then spread to the anus.
Learn more about human papillomavirus (HPV).
Sexual behaviour @(Model.HeadingTag)>
In both men and women, some sexual activities increase the risk for anal cancer. These activities include having receptive anal intercourse (receiving anal sex) and having many sexual partners. There are higher rates of anal cancer among men who have sex with men compared to the overall male population.
Weakened immune system @(Model.HeadingTag)>
The role of immunosuppression in anal cancer is not entirely clear. It is thought that a weakened immune system may not be able to get rid of an HPV infection, which can eventually lead to cancer.
History of cervical, vaginal or vulvar cancer @(Model.HeadingTag)>
Women who have been diagnosed with cancer of the cervix, vagina or vulva have a higher risk of developing anal cancer. This may be because these cancers have similar risk factors, such as an HPV infection.
Find out more about cervical cancer, vaginal cancer and vulvar cancer.
Smoking tobacco @(Model.HeadingTag)>
Studies show that smoking tobacco increases the risk for anal cancer. Smokers are several times more likely to have anal cancer compared with people who don’t smoke.
No link to anal cancer @(Model.HeadingTag)>
Significant evidence shows no link between non-cancerous tumours of the anus and a higher risk for anal cancer.
Questions to ask your healthcare team @(Model.HeadingTag)>
Expert review and references
American Cancer Society. Risk Factors for Anal Cancer. 2017: https://www.cancer.org/cancer/anal-cancer/causes-risks-prevention/risk-factors.html.
Bosman FT, Carneiro F, Hruban RH, Theise ND. WHO Classification of Tumours of the Digestive System. 4th ed. Lyon: International Agency for Research on Cancer (IARC); 2010.
Czito BG, Ahmed S, Kalady M, et al . Cancer of the anal region. DeVita VT Jr, Lawrence TS, Rosenberg SA. Cancer: Principles and Practice of Oncology. 10th ed. Philadelphia: Wolters Kluwer Health/Lippincott Williams & Wilkins; 2015: 61:842-856. http://lwwhealthlibrary.com/signin.aspx.
Grulich AE, Jin F, Poynten IM . Anal cancer. Thun MJ (ed.). Schottenfeld and Fraumeni Cancer Epidemiology and Prevention. 4th ed. New York, NY: Oxford University Press; 2018: 37:707-714.
International Agency for Research on Cancer (IARC) . Volume 90: Human Papillomaviruses . 2007 : http://monographs.iarc.fr/ENG/Monographs/vol90/mono90.pdf.
International Agency for Research on Cancer (IARC). Volume 100B: Biological agents: a review of human carcinogens. 2012: http://monographs.iarc.fr/ENG/Monographs/vol100B/mono100B.pdf.
Meyer JJ, Willett CG, Czito BG . Anal cancer. Jankowiski J, Hawk E (eds.). Handbook of Gastrointestinal Cancer. Wiley-Blackwell; 2013: 6:137-160.
National Cancer Institute. Anal Cancer Prevention (PDQ®) Health Professional Version. 2018: https://www.cancer.gov/types/anal/hp/anal-prevention-pdq.
National Comprehensive Cancer Network. NCCN Clinical Practice Guidelines in Oncology: Anal Carcinoma (Version 2.2018). https://www.nccn.org/professionals/physician_gls/pdf/anal.pdf.
National Toxicology Program . 14th Report on Carcinogens . Department of Health and Human Services ; 2016 .
Silverberg MJ, Lau B, Justic AC, et al . Risk of anal cancer in HIV-infected and HIV-uninfected individuals in North America. Silverberg MJ, Lau B, Justic AC, et al. PubMed Health. U.S. National Library of Medicine; 2012: http://www.ncbi.nlm.nih.gov/pubmed/22291097.