The human papillomavirus (HPV) is known to cause a variety of cancers, but screening guidelines and a reliable early-detection test exist for only one – cervical cancer.
“The Pap test can detect precancerous tissue and prevent cervical cancer,” said Erich Sturgis, M.D., professor of Head and Neck Surgery. “But we don’t have such a test for oropharyngeal or anal cancer, which are also linked to HPV.”
To help create such tests, Sturgis and his colleagues are conducting two clinical trials. One trial is currently enrolling women, and another will soon begin enrolling men.
Screening for anal cancers in women
Patients who have HPV-related cervical, vaginal, or vulvar carcinomas are believed to be at high risk for HPV-related anal carcinoma; however, the rates of anal cancers in these patients remain unclear. An ongoing clinical trial seeks to determine the prevalence of anal cancer in women who have cervical, vaginal, or vulvar cancer or dysplasia and compare methods of screening for HPV-related anal cancer and dysplasia.
The trial, known as the Prevalence of Anal Dysplasia and Anal Cancer in Women with Cervical, Vaginal, and Vulvar Dysplasia and Cancer (PANDA) trial, is now enrolling patients.
Kathleen Schmeler, M.D., associate professor of Gynecologic Oncology and Reproductive Medicine, and Craig Messick, M.D., assistant professor of Colon and Rectal Surgery, are the co–principal investigators of the PANDA trial.
Schmeler said that current anal cancer care, without standardized screening, is similar to the state of cervical cancer care before the advent of the Pap test.
“Most of the time, people are diagnosed with anal cancer when it is symptomatic, after the cancer is advanced and has led to another problem,” she said. “That’s how cervical cancer used to be, but since the Pap test became standard, we’re finding cervical cancer in the preinvasive phase or at an early stage. We’d like to do the same thing with anal cancer.”
Besides showing the prevalence of HPV-related anal dysplasia and cancer in this high-risk population of women, data from the study will provide information about the sensitivity and specificity of anal Pap tests, anal HPV tests, and anoscopy.
“We know there are women at high risk for anal cancer,” Schmeler said. “We want to find out how often and the most effective way to screen these women.”
Screening for oropharyngeal cancers in men
Because both oropharyngeal HPV infections and HPV-related oropharyngeal cancers are more common in men than in women, Sturgis’ trial will enroll men only, specifically those in their 50s.
“Our previous research showed a very strong link between antibodies to HPV-16 E6 and E7 antigens in the serum and oropharyngeal cancer,” Sturgis said. “We estimate that 1 to 2% of the men in our trial will test positive for these antibodies.”
Men whose serological tests are positive for antibodies to HPV-16 E6 or E7 antigens will be sent to MD Anderson for further HPV and cancer screening, as will an equal number of men who test negative for the antibodies.
“We will use some experimental approaches to see if imaging can identify early oropharyngeal cancers before they are visible to the naked eye,” Sturgis said.
One technique that may be used in the study, optical coherence tomography, is commonly used in ophthalmology but not to detect oropharyngeal cancers. Another, narrow-band imaging, has been used with endoscopy to detect early gastric tumors.
The study will also involve taking cell samples from the tonsils and the base of the tongue to look for HPV that has been integrated into the human genome. Integrated HPV is typically the first step of tumorigenesis in HPV-related cancer. Sturgis said, “This will be the first screening application of testing for integrated HPV.”
The two goals of the trial are, first, to see whether serological HPV testing in a high-risk group is an effective screening tool and, second, to see which tests are most effective for detecting early HPV-related cancers or precancers.
Read more about the role of HPV testing in cancer screening and prevention in MD Anderson’s publication OncoLog.