The cause of a disease plays a direct role in the development of the disease. ONE risk factor makes that disease more likely, but it’s not the only reason it develops. Researchers have found some risk factors that increase a person’s risk of anal cancer, but the exact cause of anal cancer is not known. It’s also important to remember that some people with anal cancer have no known risk factors.

Causes of anal cancer

• HPV infection: Human papillomavirus (HPV) infection appears to be important in the development of anal cancer, but the majority of people with HPV infections not get anal cancer. There is evidence that HPV causes many anal squamous cell carcinomas, but its role in causing anal adenocarcinomas is less certain.

• Decreased immunity: When the body is less able to fight infections, viruses such as HPV can become more active, which can allow anal cancer to develop.

• Smoking: Most people know that smoking is the main cause of lung cancer. The cancer-causing chemicals in tobacco smoke can also travel from the lungs to the rest of the body, causing other types of cancer as well.

Risk factors for anal cancer

A risk factor increases your chance of getting a disease, such as cancer. Different cancers have different risk factors. Some risk factors, such as smoking or diet, can be changed. Others, like a person’s age or family history, cannot.

Several factors can affect your risk of developing anal cancer. But having a risk factor, or even multiple risk factors, does not mean you will get cancer. Many people with risk factors will never develop anal cancer, while others with anal cancer may have few or no known risk factors.

HPV (human papillomavirus) infection

Human papillomavirus (HPV) infection is the most important risk factor for anal cancer. Most squamous cell anal cancers are associated with infection with HPV. HPV is a group of more than 150 related viruses, the same group of viruses that cause cervical cancer, and other forms of cancer. In fact, women with a history of cervical cancer (or pre-cancer of the cervix) have an increased risk of anal cancer.

• HPV can infect cells on the surface of the skin and those lining the genitals, anus, mouth and throat, but not the blood or internal organs such as the heart or lungs.
• HPV can be spread from one person to another during skin-to-skin contact. One way HPV is spread is through sexual activity, including vaginal, anal, and even oral sex.
• Different types of HPV cause warts on different parts of the body. Some cause common warts on the hands and feet; others tend to cause warts on the lips or tongue.

Infection with HPV is common, and in most cases the body can clear the infection on its own. Sometimes, however, the infection does not go away and becomes chronic. Chronic infection, especially when caused by certain high-risk HPV types, can eventually cause certain cancers, such as anal cancer.

Certain types of HPV are high risk because they are strongly associated with cancers including anal cancer, as well as cancer of the cervix, vulva and vagina in women, penile cancer in men and cancer of the anus, mouth and throat in both men and women. The high-risk subtype most likely to cause anal cancer is HPV-16. Another high-risk type is HPV-18but this is seen less often in anal cancer.

Other types of HPV can cause warts in or around the anal area and on the female and male genitalia. These are called low risk HPV because they are rarely associated with cancer.

Although there is currently no cure for HPV infection, there are ways to treat the warts and abnormal cell growth that HPV causes. HPV vaccines are also available to prevent infection with certain types of HPV and some of the cancers associated with these types.

Anal warts

People who have had anal warts are more likely to get anal cancer. This is because people infected with HPV subtypes that cause anal and genital warts are also more likely to be infected with HPV subtypes that cause anal cancer.

Have certain other cancers

Women who have had cancer of the cervix, vaginaor vulva have an increased risk of anal cancer. This is probably because these cancers are also caused by infection with HPV.

HIV infection

People who are infected with HIV (the human immunodeficiency virus), the virus that causes AIDS, are much more likely to get anal cancer than those who are not infected with this virus.

Get more information: HIV infection, AIDS and cancer.

Sexual activity

Having multiple sex partners increases the risk of infection with HIV and HPV. It also increases the risk of anal cancer. Receptive anal sex also increases the risk of anal cancer in both men and women. Because of this, men who have sex with men have a high risk of this cancer.

Smoking

Smoking increases the risk of anal cancer. The higher a person’s smoking history in a year, the higher the risk of developing anal cancer. People who currently smoke are more likely to get cancer of the anus compared to people who do not smoke or have stopped smoking. Stop smoking appears to reduce the risk.

Decreased immunity

Higher rates of anal cancer occur among people with compromised immunity, such as people with HIV/AIDS or people who have had an organ transplant and must take medications that suppress their immune system.

Gender and race/ethnicity

Anal cancer is more common in white women and black men.

Can anal cancer be prevented?

Since the cause of many cases of anal cancer is unknown, it is not possible to prevent this disease. However, there are things you can do that can lower your risk of anal cancer.

HPV vaccines

Contagion with HPV increases the risk of anal cancer. HPV infection can be present for years without causing symptoms. Even when someone doesn’t have warts (or other symptoms), they can still become infected with HPV and pass it on to someone else.

Vaccines are available that prevent certain HPV infections, including HPV-16 and HPV-18. Some may also protect against infections with other HPV subtypes, including some types that cause anal and genital warts.

These vaccines can only be used to prevent HPV infection – they do not treat an existing infection. To work best, the vaccine should be given to young children before they become sexually active.

Get more information: HPV vaccines.

Does not smoke

Smoking is a known risk factor for anal cancer. Stop smoking greatly reduces the risk of developing anal cancer and many other cancers.

Treatment of HIV

For people with HIVis very important to take medicine (known as highly active antiretroviral therapyor HAIR) to help keep HIV infection under control and prevent it from developing into AIDS. This can also lower the risk of long-term HPV infection and anal intraepithelial neoplasia (a type of anal precancer), which can help lower the risk of anal cancer. Compared to other HIV-related cancers, the number of people with HIV who have developed anal cancer while being treated with HAART has increased over the years. The reasons for this are unknown, but may be because people with HIV treated with HAART live longer.

Using a condom

Condoms can provide some protection against infection with HPV and HIV, but they do not prevent it completely. In light of this, it is unclear whether condom use can reduce the risk of anal cancer.

A study found that when condoms are used correctly, they can lower genital HPV infection rates in women – but they must be used every time sex occurs. This study did not look at the effect of condom use on anal HPV infection.

Condoms cannot provide complete protection because they do not cover all possible HPV-infected areas of the body, such as skin on the genitals or anal area. HPV can still be passed from one person to another through skin-to-skin contact with an HPV-infected area of ​​the body that is not covered by a condom. Still, condoms can provide some protection against HPV. Male condom use also appears to help genital HPV infections clear (disappear) more quickly.

Condom use is also important because it can help protect against AIDS and other sexually transmitted diseases that can be transmitted through some body fluids.