Anal Cancer Prevention (PDQ®)

Cancer prevention is action taken to lower the chance of getting cancer. By preventing cancer, the number of new cases of cancer in a group or population is lowered. Hopefully, this will lower the number of deaths caused by cancer.

To prevent new cancers from starting, scientists look at risk factors and protective factors. Anything that increases your chance of developing cancer is called a cancer risk factor; anything that decreases your chance of developing cancer is called a cancer protective factor.

Some risk factors for cancer can be avoided, but many cannot. For example, both smoking and inheriting certain genes are risk factors for some types of cancer, but only smoking can be avoided. Regular exercise and a healthy diet may be protective factors for some types of cancer. Avoiding risk factors and increasing protective factors may lower your risk but it does not mean that you will not get cancer.

Different ways to prevent cancer are being studied, including:

  • Changing lifestyle or eating habits.
  • Avoiding things known to cause cancer.
  • Taking medicines to treat a precancerous condition or to keep cancer from starting.
Anal cancer is a disease in which malignant (cancer) cells form in the tissues of the anus.

The anus is the end of the large intestine, below the rectum, through which stool (solid waste) leaves the body. The anus is formed partly from the outer skin layers of the body and partly from the intestine. Two ring-like muscles, called sphincter muscles, open and close the anal opening and let stool pass out of the body. The anal canal, the part of the anus between the rectum and the anal opening, is about 1½ inches long.


The skin around the outside of the anus is called the perianal area. Tumors in this area are skin tumors, not anal cancer.

See the following PDQ summary for more information about anal cancer:

  • Anal Cancer Treatment
Squamous cell carcinoma is the most common type of anal cancer.

In the United States, the most common type of anal cancer is squamous cell carcinoma. Studies show that human papillomavirus (HPV) infection is the main cause of this type of anal cancer.

Another type of anal cancer, called anal adenocarcinoma, is very rare and is not discussed in this summary.

In the United States, the number of new cases of anal cancer has increased in recent years.

From 2001 to 2010, new cases of anal cancer and deaths from anal cancer increased each year. The increase in new cases was slightly higher in women and the increase in deaths from anal cancer was slightly higher in men.

Avoiding risk factors and increasing protective factors may help prevent cancer.

Avoiding cancer risk factors may help prevent certain cancers. Risk factors include smoking, being overweight, and not getting enough exercise. Increasing protective factors such as quitting smoking, eating a healthy diet, and exercising may also help prevent some cancers. Talk to your doctor or other health care professional about how you might lower your risk of cancer.

The following are risk factors for anal cancer:
Anal HPV infection

Being infected with human papillomavirus (HPV) is the main risk factor for anal cancer. Being infected with HPV can lead to squamous cell carcinoma of the anus, the most common type of anal cancer. About nine out of every ten cases of anal cancer are found in patients with anal HPV infection.

Patients with healthy immune systems are usually able to fight HPV infections. Patients with weakened immune systems who are infected with HPV have a higher risk of anal cancer.

Certain medical conditions
History of cervical, vaginal, or vulvar cancer

Cervical cancer, vaginal cancer, and vulvar cancer are related to HPV infection. Women who have had cervical, vaginal, or vulvar cancer have a higher risk of anal cancer.

HIV infection/AIDS

Being infected with human immunodeficiency virus (HIV) is a strong risk factor for anal cancer. HIV is the cause of acquired immunodeficiency syndrome (AIDS). HIV weakens the body's immune system and its ability to fight infection. HPV infection of the anus is common among patients who are HIV-positive.

The risk of anal cancer is higher in men who are HIV-positive and have sex with men compared with men who are HIV-negative and have sex with men. Women who are HIV-positive also have an increased risk of anal cancer compared with women who are HIV-negative.

Studies show that intravenous drug use or cigarette smoking may further increase the risk of anal cancer in patients who are HIV-positive.

Immunosuppression

Immunosuppression is a condition that weakens the body's immune system and its ability to fight infections and other diseases. Chronic (long-term) immunosuppression may increase the risk of anal cancer because it lowers the body's ability to fight HPV infection.

Patients who have an organ transplant and receive immunosuppressive medicine to prevent organ rejection have an increased risk of anal cancer.

Having an autoimmune disorder such as Crohn disease or psoriasis may increase the risk of anal cancer. It is not clear if the increased risk is due to the autoimmune condition, the treatment for the condition, or a combination of both.

Certain sexual practices

The following sexual practices increase the risk of anal cancer because they increase the chance of being infected with HPV:

  • Having receptive anal intercourse (anal sex).
  • Having many sexual partners.
  • Sex between men.

Men and women who have a history of anal warts or other sexually transmitted diseases also have an increased risk of anal cancer.

Cigarette smoking

Studies show that cigarette smoking increases the risk of anal cancer. Studies also show that current smokers have a higher risk of anal cancer than smokers who have quit or people who have never smoked.

The following protective factor decreases the risk of anal cancer:
HPV vaccine

The human papillomavirus (HPV) vaccine is used to prevent anal cancer, cervical cancer, vulvar cancer, and vaginal cancer caused by HPV. It is also used to prevent lesions caused by HPV that may become cancer in the future.

Studies show that being vaccinated against HPV lowers the risk of anal cancer. The vaccine may work best when it is given before a person is exposed to HPV.

It is not clear if the following protective factor decreases the risk of anal cancer:
Condom use

It is not known if the use of condoms protects against anal HPV infection. This is because not enough studies have been done to prove this.

Cancer prevention clinical trials are used to study ways to prevent cancer.

Cancer prevention clinical trials are used to study ways to lower the risk of developing certain types of cancer. Some cancer prevention trials are conducted with healthy people who have not had cancer but who have an increased risk for cancer. Other prevention trials are conducted with people who have had cancer and are trying to prevent another cancer of the same type or to lower their chance of developing a new type of cancer. Other trials are done with healthy volunteers who are not known to have any risk factors for cancer.

The purpose of some cancer prevention clinical trials is to find out whether actions people take can prevent cancer. These may include eating fruits and vegetables, exercising, quitting smoking, or taking certain medicines, vitamins, minerals, or food supplements.

New ways to prevent anal cancer are being studied in clinical trials.

Clinical trials are taking place in many parts of the country. Information about clinical trials for anal cancer prevention can be found in the Clinical Trials section of the NCI Web site.

The PDQ cancer information summaries are reviewed regularly and updated as new information becomes available. This section describes the latest changes made to this summary as of the date above.

Editorial changes were made to this summary.

Physician Data Query (PDQ) is the National Cancer Institute's (NCI's) comprehensive cancer information database. The PDQ database contains summaries of the latest published information on cancer prevention, detection, genetics, treatment, supportive care, and complementary and alternative medicine. Most summaries come in two versions. The health professional versions have detailed information written in technical language. The patient versions are written in easy-to-understand, nontechnical language. Both versions have cancer information that is accurate and up to date and most versions are also available in Spanish.

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This PDQ cancer information summary has current information about anal cancer prevention. It is meant to inform and help patients, families, and caregivers. It does not give formal guidelines or recommendations for making decisions about health care.

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The information in this patient summary was taken from the health professional version, which is reviewed regularly and updated as needed, by the PDQ Screening and Prevention Editorial Board.

A clinical trial is a study to answer a scientific question, such as whether one treatment is better than another. Trials are based on past studies and what has been learned in the laboratory. Each trial answers certain scientific questions in order to find new and better ways to help cancer patients. During treatment clinical trials, information is collected about the effects of a new treatment and how well it works. If a clinical trial shows that a new treatment is better than one currently being used, the new treatment may become "standard." Patients may want to think about taking part in a clinical trial. Some clinical trials are open only to patients who have not started treatment.

Clinical trials are listed in PDQ and can be found online at NCI's Web site. Many cancer doctors who take part in clinical trials are also listed in PDQ. For more information, call the Cancer Information Service 1-800-4-CANCER (1-800-422-6237).

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The best way to cite this PDQ summary is:

National Cancer Institute: PDQ® Anal Cancer Prevention. Bethesda, MD: National Cancer Institute. Date last modified <MM/DD/YYYY>. Available at: http://cancer.gov/cancertopics/pdq/prevention/anal/Patient. Accessed <MM/DD/YYYY>.

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