Anonymous on August 10, 2011

I’ve heard that anal sex can cause anal cancer. Why is that? Does it have to do with STDs?

I’ve heard that anal sex can cause anal cancer. Why is that? Does it have to do with STDs?

answered by Ruthann M. Cunningham, MD on August 10, 2011

Thanks for your important question about sexual activity and cancer that can affect both women and men.  

You’re right. Anal sex is a risk factor for anal cancer and it does have to do with one STD in particular human papillomavirus (HPV). Why? Just like vaginal and oral sex have risks, anal sex can increase one’s chances of catching HPV in the anus. Even though anal cancer is relatively rare, an article in the journal Cancer estimates that up to 93% of anal cancers are associated with certain types of HPV. In other words, if you catch HPV and you have anal sex, you increase your risk of developing anal cancer.

So what’s the connection between HPV, anal sex and anal cancer? When our cells get infected with HPV, the virus can change the way our cells grow. If you have the kind of HPV that can cause cancer, and you have it for a long time, sometimes the virus can make tiny changes to your DNA. When that happens, the changes to your DNA can make your cells grow in ways they’re not supposed to and they become cancerous.

For a while now, doctors have known that two types of HPV are the cause of 70% of cervical cancer. It turns out that those two types of HPV are also responsible for many cancers of the anus, vulva, vagina and penis. To find out more about these HPV types, see our HPV Overview.

How can you help prevent HPV and anal cancer? As you probably know, not having sex at all is the only way to keep yourself from getting most STDs and HPV is no exception. But you can reduce your chances of getting HPV if you practice safer sex. That means using a latex condom during anal and vaginal sex, and using a dental dam or a condom during oral sex. You can protect sex toys with a latex condom, too... and always make sure to change the condom or wash the toy if you switch from the vagina to the anus or the other way around.

Remember, though, that HPV can infect areas that aren’t covered by a condom or dental dam, so safer sex isn’t foolproof. If you’re under the age of 26, you can also talk to your doctor about the HPV vaccine that can help protect you against the types of HPV that cause cancer and the types that cause genital warts.

If you are a man or a woman who has anal sex, you can also talk to your doctor about an anal Pap test. An anal Pap test is one way to monitor the cells inside the anus to see if they show any changes from cancer-causing HPV types. Not all doctors know how to perform an anal Pap test, so your doctor might refer you to a specialist to make sure it’s done correctly. If it turns out that you do have cells that look like they could be pre-cancerous, your doctor can help you look at treatment options which typically include removing the cells that don’t look right in a relatively quick procedure.

I hope this answer clears up any confusion you had about anal sex causing cancer. Again, sex doesn’t cause cancer on it’s own, but practicing safer sex can help reduce the spread of some HPV types that contribute to cancer risk.

Thanks for writing and I wish you good health.

Related info:

Ruthann M. Cunningham, MD

Dr. Cunningham is a member of the Analyte Physicans Group. She's also a member of the American College of Emergency Physicians, practicing at both Northwestern Lake Forest Hospital in Illinois and at Wheaton Franciscan All Saints Medical Center in Wisconsin. An ER physician since 2000, she regularly treats patients with STDs. Dr. Cunningham was educated at Wayne State University School of Medicine and completed her Emergency Medicine residency at Cook County Hospital in Chicago, IL.

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