Source: National Cancer Institute Research, www.cancer.gov
Cancerprevention 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:
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 1-1½ 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:
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.
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 cancerrisk 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.
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.
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.
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 intravenousdrug use or cigarette smoking may further increase the risk of anal cancer in patients who are HIV-positive.
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 organtransplant and receive immunosuppressivemedicine 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.
The following sexual practices increase the risk of anal cancer because they increase the chance of being infected with HPV:
Men and women who have a history of anal warts or other sexually transmitted diseases also have an increased risk of anal cancer.
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 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 known if the use of condoms protects against anal HPV infection. This is because not enough studies have been done to prove this.
Cancer preventionclinical 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.
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.