Anal cancer, once a relatively rare disease, is becoming more common in the Americas, Europe, and Australia, according to an October 2016 study in the International Journal of Epidemiology.
In the United States, anal cancer rates went up by 1.6 percent a year from 2004 to 2013, according to recent figures from the American Cancer Society. Between 1998 and 2014, death rates from anal cancer spiked by 3 percent a year.
Why the rise in anal cancer cases? Experts speculate that changing sexual behavior may be part of the reason. Being infected with human papillomavirus, or HPV, which is a group of more than 150 related viruses, significantly increases the risk of some cancers, including anal, mouth and throat, cervical, vaginal, and vulvar.
The HPV strains that increase anal cancer risk are sexually transmitted; the more sexual partners people have, the more likely they are to be exposed to HPV.
Infection with HPV is most closely linked to a specific form of anal cancer, known as anal squamous cell carcinoma, which is the most common form in the United States. And it’s this form of anal cancer that’s soaring in many parts of the world.
“It’s important to keep in mind that anal cancer is considered a relatively rare form of cancer, with only about 8,200 new cases in this country a year,” says William Dale, M.D., Ph.D., chairman of the Department of Supportive Care Medicine at the City of Hope Cancer Center in Duarte, Calif. “But at a time when rates for many cancers are stable or falling, the rise in anal cancers is alarming.”
What to know about anal cancer
Anal cancer is characterized by the growth of abnormal cells in the tissues of the anus. Some people equate anal cancer with cancer of the colon because of the anatomic connection, but the two diseases are quite different.
The anus comprises the very end of the large intestine. It includes the anal canal (approximately 1.5 inches), which is connected to the rectum, where fecal waste is stored, and the anal opening, which allows fecal material to be excreted. The colon comprises the final six-foot section of the large intestine up to the anal canal; the rectum comprises the final eight to 10 inches of the colon.
Like colon and rectal cancer, anal cancer is a disease of the gastrointestinal system, but its causes are more in line with genital cancers, such as cervical, vaginal, and penile.
Anal cancer risk factors
Like most cancer risks, anal cancer risk increases with age, especially after 50. Women are at slightly greater risk than men. The risk is also higher among African-American men. HPV anal infection is the leading risk factor, although most people with HPV don’t get anal cancer.
Additional risk factors include:
• History of sex with multiple partners, especially when it involves anal sex
• History of cancer, especially cervical, vulvar, or vaginal cancer
• Lowered immune function, which can be caused by human immunodeficiency virus (HIV) infection—the virus that causes AIDs—or certain drugs, such as steroids and those used by organ transplant recipients
Condom use offers some protection against HPV and HIV transmission, but studies have been relatively small in size and inconsistent in their findings.
Diagnosis and treatment
To definitively diagnose anal cancer, doctors may perform an anoscopy, inserting a hollow tube with a lens or a tiny video camera to examine the anal canal.
If abnormal tissue or a suspicious growth is found, a biopsy is performed to determine whether it’s cancerous. Imaging studies of the body such as ultrasounds or computed tomography (CT) scans are sometimes done to determine whether or how far cancer has spread.
Treatment regimens, which can include radiation, chemotherapy, surgery, or a combination of them, depends on the cancer’s extent.
Small tumors can often be removed surgically without significantly damaging nearby tissue. More extensive cancer may involve the removal of larger sections of the anus, rectum, or colon.
Fortunately, the prognosis for small tumors caught early is good. About 71 percent of patients diagnosed with the earliest stage of anal squamous cell carcinoma are alive after five years, according to the American Cancer Society.
“If you have any of the risk factors associated with anal cancer, it’s important to be alert to symptoms like persistent pain, itching, or bleeding from the anus,” Dale says.
“And it’s always wise to contact your doctor immediately if you notice anything unusual. Don’t wait for fear of embarrassment. The earlier anal cancer is treated, the better the chances of success," he says.
Signs of anal cancer
One of the earliest signs of anal cancer for nearly half of all patients is rectal bleeding, which some people may attribute to hemorrhoids, delaying diagnosis. Other symptoms include:
• Pain or a feeling of fullness around the anus
• A lump or mass at the anal opening
• Anal itching
• Abnormal discharge from the anus
• A change in bowel habits
• Swollen lymph nodes in the groin or anal area
Not everyone has symptoms. In some cases, doctors first spot signs of trouble during a routine physical examination, when they see or feel a lump or abnormality in the area of the anus.
Learn more about cancer symptoms to look out for.
Peter Jaret is the author of several health-related books, including “In Self-Defense: The Human Immune System” (Harcourt Brace), “Nurse: A World of Care” (Emory University Press), and “Impact: On the Frontlines of Public Health” (National Geographic). A frequent contributor to National Geographic, The New York Times, Reader’s Digest, Health, More, AARP Bulletin, and dozens of other periodicals, Jaret is the recipient of an American Medical Association award for journalism and two James Beard awards. He lives in Petaluma, Calif.