Anal cancer is a rare form of cancer that is associated with the human papillomavirus (HPV). Each year, approximately 8,000 people are diagnosed with this form of cancer in the United States according to the American Cancer Society. The anus, part of the rectum, is the end of the large intestine through which stool passes to exit the body.
Definition & Facts
In addition to being quite rare, anal cancer is rarely fatal. The five-year survival rate for this form of cancer is 80 percent for those who are diagnosed during stage 1 and 59 percent for those who are diagnosed after the cancer has spread, according to the American Society for Clinical Oncology.
Anal cancer is a term that specifically refers to a tumor inside the large intestine; external tumors in the area surrounding the anus are instead considered a form of skin cancer. There are five different types of invasive anal cancer, based on the five different types of cells in the anus. These include:
- Squamous cell carcinoma, the most common type, which begins in the outer lining of the anal canal and is similar to squamous cell cancers in other parts of the body. Cloacogenic carcinoma is a type of squamous cell carcinoma that occurs between the outer part of the anus and the lower part of the rectum.
- Adenocarcinoma often originates in the mucous glands under the anal lining.
- Basal cell carcinoma is a type of skin cancer that develops in the skin around the anus
- Melanoma begins in the color production cells in the skin or anal lining.
- Gastrointestinal stromal tumor - These can originate in the anus albeit rarely.
Symptoms & Complaints
- Pain or pressure in the anal area
- Rectal discharge from the rectum
- An unexplained lump
- Change in bowel habits.
It is estimated that 90% of anal cancers are caused by HPV. Therefore, it is strongly associated with activities that spread HPV, such as receptive anal intercourse. It's also more common among people who are immunocompromised, such as those with HIV. This risk group also tends to have a worse prognosis than others who develop anal cancer.
The majority of cases of anal cancer occur in those older than age 65. This disease is slightly more common among women than men over the age of 50, but occurs more often in men before age 35. Anal cancer is six times more common for single men than it is for married men. Other risk factors include frequent anal redness, swelling, and soreness; cigarette smoking; the presence of anal fistulas (abnormal openings); and having many sexual partners.
Diagnosis & Tests
Anal cancer is often detected during a routine rectal examination or procedure, such as hemorrhoid removal, though it is usually identified by a patient reporting symptoms. During a digital rectal exam, a medical provider inserts a lubricated, gloved finger into the anus to feel for any abnormalities. He or she may also perform an anoscopy or proctoscopy (examination of the anus and rectum using a short, lighted tube).
If anal cancer is suspected, the doctor will perform a biopsy. If anal cancer is diagnosed, staging tests to determine whether the cancer has spread may include abdominal and pelvic CT scan, a pelvic MRI scan, a chest X-ray, and liver function tests.
Treatment for anal cancer depends on the stage of the disease. Stage 0, carcinoma in situ, indicates that abnormal cells have been identified in the area but have not become cancer. Stage I indicates a tumor measuring 2 centimeters or smaller, while Stage II indicates a tumor larger than 2 centimeters. Stage IIIA and IIIB describes a tumor of any size that has spread to nearby lymph nodes or organs, including the rectum, urethra, vagina, or bladder. Stage IV anal cancer means that the abnormal cells have spread to distant sites throughout the body.
Treatment & Therapy
When diagnosed early, most cases of anal cancer are highly treatable. Because this form of cancer spreads slowly, it is found before metastasizing in most cases.Most cases of anal cancer are successfully treated with a combination of chemotherapy and radiation. If these modalities are not effective, surgery may be necessary.
In some cases where the cancer has not spread, the surgeon may be able to perform a local resection, in which only part of the anus is removed and the anal sphincter is preserved so that the patient can still control his or her bowel movements.
In other cases, the entire anus, rectum, and lymph nodes must be removed. This results in the need for a colostomy, a disposable bag in which waste is collected outside the body.Surgical treatment for anal cancer is more commonly needed among patients with HIV, since their immune systems may not be able to handle the necessary dosage of chemotherapy or radiation.
Prevention & Prophylaxis
In addition, lifestyle changes can help reduce one's risk for developing anal cancer. These include quitting smoking, limiting the number of sexual partners, and practicing safe sex, including condom use during both anal and vaginal intercourse.
If one is at high risk for developing anal cancer, early detection is the best way to find the disease in its most treatable stages. Individuals should talk with their doctors about regular screening that can help detect abnormal cells in the anus before they develop into cancer.