What are anal cancer statistics?
Anal cancer is far more rare than colorectal cancer. Anal cancer will be found in about 5,530 women and 2,770 men in 2019. It will result in about 1,280 deaths in 2019. It is more common today than it was 30 years ago.
What causes anal cancer?
Anal cancer is most commonly caused by infection of the anal lining tissues by a high-risk type of human papillomavirus (HPV) such as HPV-16. It is also more common in people with weakened immune systems, such as those with HIV (human immunodeficiency virus, the virus that can lead to AIDS). Cigarette smokers also get more anal cancer than nonsmokers. Other risk factors for anal cancer usually will be those associated with the likelihood of acquiring HPV infection. Certainly, there are also cases of anal cancer for which doctors can find no certain cause.
What are the risk factors for anal cancer?
Anal cancer risk factors include the following:
- Age over 50
- Human papillomavirus (HPV) infection
- Many sexual partners
- Receptive anal intercourse/anal sex
- Conditions that impair the immune system including HIV viral infection and immunosuppressive medicines
- History of other pelvic cancers caused by HPV infection
- Recurrent anal irritation with pain and redness
- Race and gender: Anal cancer is more common in women than men in most ethnic groups. In African Americans, it is more common in men than women.
What are the symptoms and signs of anal cancer?
The symptoms and signs of anal cancers may include one or more of the following:
- A lump or mass near the anus
- A tumor or lump found on self-examination
- Anal bleeding
- A sense of pressure or foreign body sensation in the anal area
- A change in bowel habits, such as constipation, incontinence (leakage of bowel movements), and/or diarrhea
- Anal discharge, which may be jelly-like and comprised of mostly mucus (It may also have a white or yellow appearance.)
- Yellow discharge or a white discharge from anus
- Mucus in stool
- Itchy anus: Anal pruritus is a condition where the anus feels itchy. Some people who get anal cancer report having an itching anus. However, there are a number of other conditions that can cause an itchy anus, including diet, medications, and bowel leakage.
- Painful defecation, anal pain, or pain in the perianal area
Many of these symptoms are easily mistaken for hemorrhoids. When first encountered, these symptoms are best evaluated by a health care professional. Even if a person has known hemorrhoids, a change in such symptoms and signs, such as their failure to resolve or a worsening, should also prompt examination.
Most anal cancer is found at an early or localized stage. In the unfortunate event that the disease is already spread outside of the anus, then symptoms and signs of more advanced disease can develop. These can include
What's involved with anal cancer screening (early detection)?
Looking for a disease or condition in people with no symptoms or signs is called screening. Screening is performed to find cancers at an early stage when treatment can be most beneficial. As anal cancer is rare, routine screening of the general public for this condition is not recommended.
In groups at higher risk for anal cancer and especially precancerous lesions called anal intraepithelial neoplasia (AIN), screening is appropriate. This includes men who have sex with men regardless of HIV status, women with histories of cervical and vulvar cancers, all HIV positive patients, post-transplant patients on immunosuppressive medicine, and those with a history of anal warts. Anal warts are not themselves considered precancerous, but imply HPV infection is present. Certain dangerous HPV subtypes may indicate the presence of cancer or lead to cancer development.
The screening technique for AIN is called an anal pap smear and uses the same technique used for women's pap smears. A swab is taken from the anal canal and a smear from the swab is submitted for microscopic evaluation by cytology technique. More recently, lab techniques are used to measure the presence and levels of the dangerous HPV (16 and 18) subtypes or the presence of mutations.
Screening frequency recommendations are still being established. For now, men who have sex with men and are HIV negative should be screened every 2-3 years. If they are HIV positive, then they should be screened yearly. If an anal pap smear is positive for AIN, the patient should be referred to a surgeon for a biopsy.
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Edge, S.B., et al. "Anal Cancer." AJCC Cancer Staging Manual, 7th Ed. New York, NY: Springer, 2010.
"NCCN Clinical Practice Guidelines in Oncology: Anal Carcinoma." Version 1.2017.
"PDQ National Cancer Institute Summaries: Anal Cancer." 2017.