Based on the protective effects of intrauterine devices against endometrial cancer, researchers hypothesized that IUDs may also have a protective effect against cervical cancer. However, results from epidemiological and clinical studies to date have been inconclusive.
Based on the protective effects of intrauterine devices against endometrial cancer, researchers hypothesized that IUDs may also have a protective effect against cervical cancer. However, results from epidemiological and clinical studies to date have been inconclusive. Thus, Dr Xavier Castellsagu of the Cancer Epidemiology Research Program at the Institut Catal d'Oncologia in Catalonia, Spain, and colleagues sought to better understand the relationship between IUDs and cervical cancer. The results of their study were published in The Lancet Oncology.
Castellsagu and colleagues conducted a pooled analysis of individual data collected from two large studies on human papillomavirus and cervical cancer, one included a series of HPV prevalence surveys and the other included a series of case-control studies of HPV and cervical cancer. The studies involved almost 20,000 women across Europe, Asia and South America.
The researchers examined the potential effect of IUD use on cervical HPV infection by looking at two groups-women in the control group in the case-control studies and women recruited in the HPV prevalence surveys. Castellsagu et al. did not find an association between use of IUDs and cervical HPV-DNA detection among the women in the control group (odds ration=0.95). In addition, the researchers failed to find a significant association between IUD use and cervical HPV in the 16 surveys they examined.
However, Castellsagu and colleagues found an inverse association between use of IUDs and cervical cancer risk; this association was found for all study areas with the exception of Morocco. Specifically, the researchers found a combined IUD prevalence of 13.0% and 22.5% for women with cervical cancer and women in the control group, respectively. Furthermore, the strong and significant inverse association was found between ever using an IUD and cervical cancer risk for all cervical cancers combined after adjusting for relevant covariates (OR=0.55). They also found that the risk for cervical cancer was reduced by about half in the first year of IUD use, and the association was maintained with longer durations of use.
“The associations found in our study strongly suggest that IUD use does not modify the likelihood of prevalent HPV infection, but might affect the likelihood of HPV progression to cervical cancer. Thus, IUD use could possibly be regarded as a protective cofactor in cervical carcinogenesis,” the study authors explained. “One of the mechanisms by which IUDs might exert this protective effect is through the induction of a reactive, chronic, low-grade, sterile inflammatory response in the endometrium, endocervical canal, and cervix that could modify, via changes in the local mucosal immune status, the course of HPV infections.”
In an accompanying editorial, Dr Karl Ulrich Petry, head of the department of gynecology and obstetrics at Klinikum Wolfsburg in Germany, noted the clinical relevance and importance of this study. “At first glance, the main implication of this finding is that it provides a high level of evidence to contradict a widespread assumption that IUD use increases the risk of cervical cancer,” he noted. “However, restored confidence in the safety of IUDs is really just a secondary result. The protective effect of IUD use challenges some key elements in the current model of the natural history of cervical cancer.”
CastellsaguÃ© X, DÃaz M, Vaccarella S, et al. Intrauterine device use, cervical infection with human papillomavirus, and risk of cervical cancer: a pooled analysis of 26 epidemiological studies. Lancet Oncol. 2011; Sep 12 [Epub].
Petry KU. Loops in the natural history of cervical cancer. Lancet Oncol. 2011; Sep 12 [Epub].