By Michael Smith, North American Correspondent, MedPage Today
Published: January 06, 2011
Reviewed by Zalman S. Agus, MD; Emeritus Professor
University of Pennsylvania School of Medicine.
Male circumcision can reduce the risk that female partners will acquire human papillomavirus (HPV), researchers reported.
Women in two large trials of circumcision had a lower incidence and prevalence of HPV if their partners got the procedure, according to Aaron Tobian, MD, of Johns Hopkins University, and colleagues.
But protection was only partial so other safe sex practices remain important, Tobian and colleagues reported online in The Lancet.
The findings come from two parallel but independent trials in Rakai, Uganda, whose main purposes were to establish the effect of circumcision on the risk of men catching HIV in one case and the risk of transmitting the virus to their partners in the other.
The researchers separately contacted partners of trial participants who were married or in a long-term relationship and asked them to take part in a follow-up study looking at the effect of circumcision on the prevalence and incidence of high-risk strains of HPV.
Earlier studies had shown that the procedure reduces both prevalence and incidence in men, and observations had suggested it might have a beneficial effect in women, Tobian and colleagues noted.
To find out, they enrolled 648 partners of men in the circumcision group, and 597 partners of men in the control group between 2003 and 2006. The women were asked to provide vaginal swabs for HPV testing at baseline, 12 months, and 24 months.
At the two-year follow-up, data were available for 544 women in the intervention group and 488 in the control group.
Of those, 151 women in the intervention group (27.8%) had a high-risk HPV infection, defined as one or more of the genotypes 16, 18, 31, 33, 35, 39, 45, 51, 52, 56, 58, 59, 66, and 68.
In comparison, 189 women in the control group (38.7%) had a high-risk HPV infection, leading to a prevalence risk ratio of 0.72 (95% CI 0.60 to 0.85, P=0.001).
Incidence of high-risk HPV infection during the trial was also lower in the intervention group than in the control group — 20.7 infections per 100 person-years versus 26.9, yielding an incidence rate ratio of 0.77 (95% CI 0.63 to 0.93, P=0.008).
Given that persistent high-risk HPV infection is a recognized cause of cervical malignancies, the finding “accords with observational studies that show lower rates of cervical cancer associated with male circumcision,” the researchers argued.
But the study did not assess cervical neoplasia directly, they noted.
Tobian and colleagues cautioned that men and women in the study were in stable relationships and did not have HIV at baseline, so the results may not apply to other populations. The analysis may also have underestimated incidence, they cautioned, because infections acquired and cleared between the yearly follow-up points would have been missed.
An estimate of protection against cervical disease as a result of circumcision can’t be made, according to Anna Giuliano, PhD, of the H. Lee Moffitt Cancer Center in Tampa, Fla., and colleagues.
But the results do add weight to programs that promote circumcision in countries without cervical screening programs, Giuliano and colleagues argued in an accompanying commentary.
The procedure offers limited protection against most high-risk types, they noted, while the HPV vaccine is highly effective, but only against a limited number of genotypes. “The two interventions are likely to have important synergistic effects,” they concluded.
The study was supported by the Bill & Melinda Gates Foundation, the NIH, and the Fogarty International Center.
One author reported a financial link with Roche Molecular Diagnostics, which makes the HPV genotyping test used in this study. All other authors declared they had no conflicts of interest.
The commentary authors reported financial links with Merck, GlaxoSmithKline, and Roche.