STANFORD, Calif. - Rates of cervical cancer dropped by 78 percent once women started receiving yearly pap smears in the 1940s. Now Mark Welton, MD, associate professor of surgery at Stanford University Medical Center, hopes to achieve similar success for anal cancer, which is believed to be caused by the same virus as cervical cancer.
"The other option is to not treat these people and let them get cancer," Welton said.
Welton has developed an approach for detecting and removing potentially cancerous cells before anal cancer develops. He will describe his success with this technique June 8 at the annual meeting of the American Society of Colon and Rectal Surgeons in Chicago.
"Anal cancer is a problem that's under-recognized," Welton said. "Doctors think it only applies to a small group of people." However, Welton said that in HIV-negative men who have sex with men, anal cancer is as common as cervical cancer was in women before pap smears became widely used - about 350 cases per million. The rate doubles among HIV-positive men who have sex with men, he said.
Welton said those at high risk for anal cancer include women who have had cervical cancer or a precancerous condition called cervical dysplasia, and their partners. Risks also are higher in people who are immune-suppressed, such as those who are HIV positive or who are on immune-suppressing drugs after an organ transplant.
Anal and cervical cancers are believed to be caused by the human papilloma virus - the same virus that results in genital warts. Almost all people are infected by the virus through sexual contact, but their immune systems eliminate the virus before any damage is done. However, some strains of the virus are more tenacious than others, and immune-suppressed individuals have a harder time eliminating HPV from their systems. In these people, the virus can cause dysplasia (or abnormal development), which, if not treated, may go on to become cancerous.
If cervical dysplasia is found after a pap smear, the doctor burns the affected tissue to destroy those cells, preventing cancer from forming. Welton believes a similar technique could prevent anal cancer. Not all doctors, however, agree that HPV is at the root of the cancer. Most doctors instead simply treat anal cancer once it develops rather than take a preventive approach.
"There's no other organ where we wait until cancer develops," Welton said. He pointed to the cervix, breast, colon and skin as examples of organs in which doctors remove precancerous cells before they go on to form tumors.
Welton argues that anal and cervical tissues look the same under the microscope, are both susceptible to HPV infection and develop similar forms of dysplasia. What's more, mild dysplasia appears to progress to severe dysplasia in a similar fashion in the two tissues. "I've spent my career arguing that cervical and anal cancer are similar," Welton said.
For individuals at high risk of developing anal cancer, Welton administers a series of chemicals that turn HPV-infected cells white, tan or yellow, and stains normal tissue black in a procedure he has dubbed "anal cartography." When he sees any of the light-colored cells - those infected with the virus - Welton takes a small sample for analysis and then burns the remaining tissue to kill potentially cancerous cells. "By doing this we avoid cancer and chemotherapy," he said.
In a study published in April, Welton showed that the procedure is safe, doesn't result in incontinence and doesn't decrease sexual enjoyment. What's more, none of the patients who had high-grade dysplasia and who were treated by Welton ultimately developed cancer. "Nobody else can say that," Welton said. In his talk, Welton will argue that all individuals at high risk should receive anal pap smears to detect precancerous cells. When doctors detect dysplasia, they should destroy the tissue in the same way they treat precancerous cervical tissue.
Stanford University Medical Center integrates research, medical education and patient care at its three institutions - Stanford University School of Medicine, Stanford Hospital & Clinics and Lucile Packard Children's Hospital at Stanford. For more information, please visit the Web site of the medical center's Office of Communication & Public Affairs at http://mednews.