Is Anal Cancer Preventable?

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Gay Male Couple Holding Hands. Gary John Norman/Getty Images

Anal cancer isn't the most common cancer caused by HPV, but it can be devastating. That's why it's important to know that, like many HPV associated cancers, anal cancer is largely a preventable illness. By choosing to get an HPV vaccine, practicing safe anal sex, and being screened appropriately, many people who would otherwise be at risk for anal cancer should be able stop it in its tracks.

Who Is At Risk for Anal Cancer?

The vast majority of anal cancers, somewhere between 80-90 percent, are caused by HPV infection.

HPV is a sexually transmitted virus that has been associated with a number of types of cancer, including cervical cancer, oral cancer, and penile cancer. Transmission of the virus can be reduced both through the use of barrier methods during sex and through vaccination against the most common cancer causing variants of the virus.

Although anal cancer is often thought of as a disease of gay men, research suggests that anal cancer is actually more common in women. However, men who have sex with men have a highly elevated risk of developing anal cancer compared to other populations, particularly if they are infected with HIV. HIV infection is associated with increased risk of a number of HPV associated cancers in addition to other diseases.

In addition to HPV and HIV infection, risk factors for anal cancer include:

  • a history of cervical, vaginal, or vulvar cancer
  • immune suppression that is not caused by HIV
  • smoking cigarettes

How Can Anal Cancer Be Prevented?

The most effective way to prevent anal cancer is to reduce the likelihood of anal HPV infection. There are, basically, three ways to do that. The first is for a person to limit their number of sexual partners, although HPV is common enough that most sexually active individuals will be exposed at some point in their lives.

The second is to always use condoms or other barriers for anal sex or oral-anal contact. The third is to encourage individuals to be vaccinated against HPV.

Recent clinical trials have shown that vaccination against the two most common cancer-causing types of HPV can significantly reduce the risk of anal cancers and anal pre-cancers. For individuals who complete the entire vaccine series the risk may be reduced by as much as 75 percent! However, vaccination can not, and should not, be used in isolation. Since it only protects against certain strains of the virus, it doesn't provide perfect protection. Therefore, it's still a good idea to consistently practice safe anal sex - to protect not just against anal cancer but against other STDs.

For individuals who are HIV positive, it's also a good idea to stay on top of your medication. Several studies have suggested that anal cancer is less common in individuals whose HIV infection is well controlled, as evidenced by high CD4 counts and low viral loads.

How Much Should I Worry About Anal Cancer?

Anal cancer is a relatively rare type of cancer and most people are at relatively low risk. However, if you regularly have receptive anal sex (i.e. "bottom"), it's a good idea to talk to your doctor about your risk and whether you should be screened for anal HPV or pre-cancerous changes. This is particularly true for individuals who have or are at high risk of HIV, have a number of different sexual partners, or do not reliably practice safer sex.

Sources:

Medford, R.J. & Salit, I.E. (2014)  Anal cancer and intraepithelial neoplasia: epidemiology, screening and prevention of a sexually transmitted disease CMAJ cmaj.140476; e-published ahead of print

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