Risk factors for anal cancer include certain sexually transmitted infections.
Bleeding with bowel movements, pain, and sometimes itching around the anus are typical symptoms.
A manual examination, sigmoidoscopy or colonoscopy, and a biopsy are done to verify the diagnosis.
Treatment may involve either surgery alone or a combination of radiation therapy and chemotherapy or radiation therapy and surgery.
Anal cancer develops in the skin cells of the immediate area around the anus or in the lining of the transitional zone between the anus and the rectum (the anal canal). Unlike in the rectum and the large intestine, in which cancers are almost always adenocarcinomas, cancers of the anus are primarily squamous cell carcinomas.
Anal cancer occurs in about 9,760 people in the United States each year and causes about 1,870 deaths. Anal cancer is more common among women.
Risk factors for anal cancer include the following:
Human papillomavirus (HPV) infection (genital warts)
Receptive anal intercourse
Chronic fistulas
Radiation therapy on anal skin
Lymphogranuloma venereum infection
Smoking
Symptoms of Anal Cancer
People with anal cancer often experience bleeding with bowel movements, pain, and sometimes itching around the anus. About 25% of people with anal cancer have no symptoms. In this instance, the cancer is found only during a routine examination.
Diagnosis of Anal Cancer
A doctor's evaluation
Sigmoidoscopy or colonoscopy
Biopsy
To diagnose anal cancer, a doctor first inspects the skin around the anus for any abnormalities. With a gloved hand, the doctor probes the anus and lower rectum, checking for any portions of the lining that feel different from surrounding areas. A flexible sigmoidoscope (a short viewing tube with a camera on the end) is used to evaluate the anus and rectum. An anoscope (a small rigid tube equipped with a light) may be inserted several inches into the anus to assist with examination.
The doctor then removes a sample of tissue from an abnormal area and examines it under a microscope (called a biopsy).
Once anal cancer is diagnosed, other imaging tests, such as computed tomography (CT) or magnetic resonance imaging (MRI), are done to determine whether the cancer has spread (metastasized).
If people have bleeding, doctors may do a colonoscopy to look for a coexisting colon cancer. During a colonoscopy, the entire large intestine is examined. A colonoscopy may be done even in people with who have obvious hemorrhoids (twisted veins located in the wall of the rectum and anus), which can cause bleeding.
Treatment of Anal Cancer
Combination of chemotherapy and radiation therapy (called chemoradiation)
Sometimes surgery
The treatment of and prognosis for anal cancer depend on the extent of the cancer.
Chemoradiation is usually done first. Tumors continue to shrink for up to 6 months after chemoradiation is completed.
Surgery is done in people whose cancer does not go away after chemoradiation or goes away and comes back. With surgery, the doctor must be careful not to interfere with the functioning of the muscular ring that keeps the anus closed (the anal sphincter). A sphincter that does not function properly could lead to loss of control over bowel movements (fecal incontinence).
