Just as use of Pap smears has led to a dramatic drop in cervical cancer, so screening for anal cancer among HIV-positive gay and bisexual men would save many lives at a reasonable cost, according to a new study published in the Journal of the American Medical Association (JAMA).
The study predicts that use of a simple and inexpensive procedure, comparable to a Pap smear, would lead to both early detection of pre-cancerous lesions among high-risk men and allow for early treatment of a type of cancer known as anal squamous cell cancer.
About 35 HIV-negative gay men per 100,000 develop this form of anal cancer every year, according to available statistics. Among HIV-positive gay men, the rate is estimated to be about twice as high.
By comparison, about 40 women per 100,000 contracted cervical cancer every year in the U.S. before the Pap smear was in widespread use. Today, only about eight women per 100,000 get cervical cancer. The hope is that a simple, early screening procedure for anal squamous cell cancer would lead to a similar drop in disease and death.
"Unlike other cancers in HIV-positive men, this cancer is potentially preventable," says Joel Palefsky, M.D., professor of laboratory medicine at the University of California San Francisco and senior author of the JAMA paper. No one knew that cervical cancer was preventable before the use of Pap smears as a screening aid became widespread in the 1960s, Palefsky adds.
Leader of the study and first author on the JAMA paper is Sue J. Goldie, M.D., M.P.H., assistant professor of health policy and decision science in the Department of Health Policy and Management at Harvard School of Public Health.
The new study draws on scientific information gained from cervical cancer screening and is based on epidemiological data from large samples of at-risk men in San Francisco and Seattle.
The researchers predict that annual anal Pap smear screenings, along with follow-up biopsies and surgeries for those whose screenings warrant them, would cost about $16,000 per year of life gained, adjusted for quality of life. By comparison, annual mammography has been reported to cost approximately $120,000 per year of life gained.
According to the study's projections, screening annually would be the most beneficial and cost-effective strategy. Screening less frequently would be less effective at detecting cancer or precancerous lesions, while screening more often would provide little added benefit for its higher cost.
The brief procedure involves inserting a swab into the anal canal and removing it. It causes mild discomfort.
The study does not conclude that practitioners should immediately begin offering the simple screening procedure.
"This study provides an important piece of additional evidence that anal Pap screening should be done for this at-risk population," Palefsky says. "However, before we proceed, we must first replicate the data we have from Seattle and San Francisco in other populations, to be able to dismiss the possibility that the disease pattern in these cities is unique."
Also, more health workers will need to be trained, both in performing biopsies when the screening test shows abnormal cells, and in surgical procedures to treat the precancerous lesions, the study notes. At present, surgery for this cancer is difficult and expensive.
Co-authors of the study, along with Goldie and Palefsky, are Karen M Kuntz, Sc.D., assistant professor of decision science, Milton C. Weinstein, Ph.D., Henry J. Kaiser Professor of Health Policy and Management, both in the health policy and management department at Harvard School of Public Health, and Kenneth A. Freedberg, M.D., M.Sc., associate professor of medicine in the department and also at the Boston Medical Center and Boston University School of Medicine and School of Public Health. Also, Mark L. Welton, M.D., assistant professor of surgery at UCSF.
The study was funded by the Harvard Agency for Health Care Policy and Research, and by the National Cancer Institute.