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Anal Cancer

Although rare, anal cancer is becoming more prevalent in the United States and many other developing countries. The condition develops in the tissues of the anus, which is a short tube that connects the lower part of the large intestine, known as the rectum, to the outside of the body. The anus allows the controlled disposal of body waste during bowel movements.

Like cervical cancer, the principal cause of anal cancer is human papillomavirus (HPV), a common virus that causes changes in the skin. Anal HPV infection is most commonly acquired through anal intercourse, but it can also be acquired from other genital areas that are infected, particularly from the vulva in women, or from the penis in men. Fingers and toys can probably lead to anal HPV infection as well.

Research suggests that sexually active individuals, both men and women, may be at risk for HPV. The good news is that only a fraction of people with anal HPV infection will develop a lasting case of anal intraepithelial neoplasia (AIN) — a precursor to anal cancer — and even fewer will develop anal cancer.

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Other risk factors for anal cancer include:

  • Men and women with a history of anal intercourse
  • Men and women with a history of perianal warts, which are found outside the anus
  • Women with a history of vulvar warts, which are found outside the female genitals
  • Men and women who are chronically immunocompromised, such as those taking immunosuppressive medications, and those who are HIV positive, or those have received organ transplants

Additional risk factors include being over 50 years of age, having many sexual partners and smoking, which increases a person's chance of developing HPV.

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Patients with invasive anal cancer experience a wide variety of symptoms, but at the earliest stage of cancer, patients often have no symptoms. The most common symptoms include:

  • Pain or tenderness in the area around the anus, which can be constant or occur only with bowel movements or receptive sex
  • Bleeding with bowel movements or following sex that is different from normal
  • Lump or hard area on the outside of the anal area that appears to be increasing in size
  • Itching or discharge from the anus
  • Pain or a sense of fullness and constant need to go to the bathroom, or both, which may occur as tumors grow and begin to invade the sphincter muscle

If you are at risk of anal cancer or are experiencing symptoms, it is important to contact your doctor and be examined promptly. If cancer is detected, an early diagnosis will help improve outcomes and smaller tumors can be treated more effectively with fewer side effects.

In making a diagnosis of anal cancer, your doctor will first start by recording your medical history. This includes information about your general health, immune status, medications you are taking, and if you are HIV+, your current viral load and CD4+ lymphocyte count.

Your doctor will also ask about any history of anal warts, dysplasia or anal problems. You will also be asked about having a heart valve abnormality that is severe enough to warrant taking antibiotics when you have your teeth cleaned to prevent heart valve infections. If this applies to you, you will be prescribed antibiotics before having any biopsies, which may be part of your cancer diagnosis.

Next, your doctor will ask you to describe any symptoms you are currently experiencing, such as anal itching, discomfort, irritation, pain or difficulty with bowel movements or any problems that occur with anal sex, if applicable.

Your doctor may also recommend the following tests to make a definite diagnosis of anal cancer:

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Treatment for anal cancer depends on many factors, including the location, type and stage of your tumor, as well as your age, health and personal preferences. Your doctor will discuss treatment options in detail with you and design the most effective plan for your condition.

Invasive anal cancer is curable in many patients, particularly when it is diagnosed early and tumors are small. Anal cancers are most commonly treated with a combination of chemotherapy and radiation, which causes tumors to completely regress in 80 to 90 percent of cases.

Surgery may be required for some cancers that do not respond to chemotherapy and radiation, or for those that recur after treatment with chemotherapy and radiation.

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Reviewed by health care specialists at UCSF Medical Center.