By Ruthann M. Cunningham, MD,
I’ve heard that anal sex can cause anal cancer. Why is that? Does it have to do with STDs?
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.