Human papillomavirus (HPV) infection is strongly associated with anal cancer. HPV infection, the various factors associated with it, and smoking are all risk factors for anal cancer. There are several steps you can take to help prevent this condition.

Anal cancer is cancer that begins in the anus. This is the area connecting your large intestine to the outside of your body through which stool passes during a bowel movement.

Having anal cancer can lead to symptoms like anal bleeding, pressure or pain around the anus, and changes in your bowel habits. Anal cancer also has the potential to spread into other nearby tissues as well as distant tissues (metastasis).

HPV infection is strongly associated with anal cancer. Below, we’ll explore the causes and risk factors of anal cancer. We’ll also answer some frequently asked questions.

Like other cancers, anal cancer happens when cells begin to grow uncontrollably and invade surrounding tissues. This occurs due to DNA changes that affect cell growth and division.

Although doctors don’t know the exact cause of anal cancer, HPV infection is strongly linked with it. An estimated 80–85% of anal cancer diagnoses are associated with HPV.

HPV is the most common sexually transmitted infection in the United States. Most HPV infections resolve without symptoms, but some can cause genital warts or cancer.

Doctors often refer to the types of HPV associated with cancer as “high risk”. The type of HPV most commonly associated with anal cancer is HPV16.

HPV infection is a major risk factor for anal cancer.

In addition to having a known HPV infection, other HPV-related risk factors for anal cancer include:

  • Cancer history: Having a personal history of other cancers strongly linked to HPV — such as cervical cancer, vulvar cancer, or vaginal cancer — increases your chance of developing anal cancer.
  • Anal warts: The types of HPV that cause anal warts are different than those that cause anal cancer, but having an HPV type associated with anal warts could mean that you have a higher chance of contracting one that’s linked with cancer.
  • Weakened immune system: Having a weakened immune system means that your body may be less able to respond to infections like HPV. Potential causes of a weakened immune system include:
    • previously receiving an organ transplant
  • Sexual factors: Some factors related to sexual activity can also increase your likelihood of HPV and can, therefore, raise your chance of having anal cancer. These include having multiple sexual partners and having receptive anal sex.

Smoking is also an independent risk factor for anal cancer. This is because tobacco smoke contains many cancer-causing chemicals.

However, smoking can also negatively affect your immune system, including reducing its ability to resist infections. In fact, compared with those who’ve never smoked, current smoking is associated with a higher prevalence and persistence of HPV.

Yes. Since HPV is the main cause of anal cancer, one of the best ways to prevent anal cancer is to get the HPV vaccine.

The HPV vaccine protects against HPV strains that cause genital warts as well as those most commonly associated with cancer, including HPV16.

The Centers for Disease Control and Prevention (CDC) recommends that children ages 11–12 years old receive two doses of the HPV vaccine 6–12 months apart. However, teenagers and adults can get the vaccine as well.

Other ways you can lower your likelihood of developing anal cancer include:

The symptoms of anal cancer may include:

Many of these symptoms can be due to other conditions, like hemorrhoids or anal fissures. However, if you have any of the symptoms above, it’s important to discuss them with a doctor.

Yes. A colonoscopy can detect irregularities in your anus that may be associated with anal cancer. However, additional testing — such as analysis of a biopsy sample — is needed to confirm a diagnosis of anal cancer.

Anal cancer isn’t common. It’s estimated to make up only 2.5% of all cancers affecting the digestive tract.

Doctors will make about 10,540 new diagnoses of anal cancer in the United States in 2024.

Yes, anal cancer can be fatal. However, your outlook depends on many factors, like the stage of the cancer, how it responds to treatment, and your age and overall health.

According to the National Cancer Institute, the 5-year survival rates for anal cancer diagnosed in 2013–2019 were:

  • 70.4% overall
  • 83.7% when anal cancer was only in the anus
  • 67.5% when anal cancer had spread regionally
  • 26.2% when anal cancer had metastasized to more distant tissues

Yes. It’s possible to eliminate anal cancer, particularly early stage anal cancer. More advanced cancers have spread farther and are more challenging to treat.

The main treatment types for anal cancer are surgery, when possible, and a combination of chemotherapy and radiation therapy (chemoradiation).

The exact cause of anal cancer is still unknown. However, HPV infection is strongly associated with anal cancer. It’s also the major risk factor for anal cancer. Smoking is another risk factor for anal cancer.

Getting the HPV vaccine can help prevent anal cancer, as it protects against the type of HPV that’s most associated with anal cancer. Quitting smoking and using a condom or another barrier method during sex are also important for prevention.

The outlook for cancer in general is better with early detection and treatment. Contact a doctor if you start having new or concerning symptoms, like anal bleeding, pain or itching around your anus, or changes in your bowel habits.