Just as use of Pap smears has led to a dramatic drop in cervical cancer, so screening for anal cancer among gay and bisexual men would save many lives at a reasonable cost, according to a study conducted at the School of Public Health and University of California at San Francisco (USCF). Anal squamous cell cancer and cervical cancer are similar diseases, both caused by a sexually transmitted virus called human papillomavirus (HPV).
The study, led by Sue Goldie, assistant professor at the School of Public Health Harvard Center for Risk Analysis, predicts that the use of a simple and inexpensive procedure, comparable to a Pap smear, would lead to detection of pre-cancerous lesions among high-risk, HIV-negative men and allow for removal of these lesions and early treatment of anal cancer. A study by the same scientists last year reported similar findings for HIV-positive gay men.
The new research is reported in the June 1 issue of The American Journal of Medicine. The issue includes a supporting editorial written by Paul Volberding, UCSF professor of medicine at the UCSF-affiliated San Francisco General Hospital Medical Center. Senior author of the study, Joel Palefsky, says, “No one knew that cervical cancer was preventable before the use of Pap smears became widespread in the 1960s and cut the incidence of the disease by 80 percent. The hope is that a simple, early screening procedure for HPV-induced anal cancer would lead to a similar drop in disease and death.” Palefsky is professor of medicine and of laboratory medicine at UCSF.
Available statistics indicate that up to 35 gay men per 100,000 develop this form of anal cancer per year, a figure comparable to the 40 women per 100,000 who contracted cervical cancer in the United States before the use of Pap smears. The new model, based on current clinical evidence, predicts that every two- to three-year anal Pap smear screening 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.
The analysis draws on the scientific information gained from cervical cancer screening and is based on health and other epidemiological data from large samples of at-risk men in San Francisco and Seattle. The study does not conclude that practitioners should immediately begin offering the simple screening procedure. The investigators caution, “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.”
They also note that although the screening test is simple and appears reliable, it is not in widespread use. Training of medical workers will have to be expanded to make the test more widely available. In addition, research is needed to determine the optimal surgical procedures to treat the precancerous lesions.