Just in: IUDs reduce cervical cancer risk
Add more research to your database of information on intrauterine devices (IUDs): Results of a new international analysis indicate that using an IUD might lower cervical cancer risk in device users.1
To perform the study, researchers designed a pooled analysis of individual data from two large studies by the International Agency for Research on Cancer, an international collaboration on cancer research, and the Institut Català d'Oncologia, a Spanish-based oncology research program. One study included data from 10 case-control studies of cervical cancer done in eight countries, and the other included data from 16 human papillomavirus (HPV) prevalence surveys of women from the general population in 14 countries. A total of 2,205 women with cervical cancer and 2,214 matched control women without cervical cancer were included from the case-control studies, and 15,272 healthy women from the HPV survey.
After controlling for health and behavioral factors, the researchers report that using an IUD reduced the risk of cervical cancer by 45%, compared with never using one. The protective effect was apparent in the first year of use and continued for as many as 10 years, the researchers note.1
Previous studies have associated IUD use with a reduced risk of endometrial cancer, but the device's effect on the risk for cervical cancer had not previously been determined. The new study is the largest one to examine the association between IUDs and cervical cancer risk, and it also is the first one to include HPV in its analysis.
Check possible causes
While researchers report IUD use did not affect the risk of HPV infection, it was associated with a lower risk of cervical cancer for both major cervical cancer types, the researchers report. The likelihood of developing squamous-cell carcinoma was reduced by 44%, with risk for adenocarcinoma or adenosquamous carcinoma reduced by 54%. While study data suggest that IUD use does not modify the likelihood of prevalent HPV infection, it might affect the likelihood of HPV progression to cervical cancer, researchers note.1
What are possible explanations for the protective effect of IUDs? The researchers suggest the process of device insertion or removal might destroy precancerous lesions. IUD use might also induce chronic mucosal inflammation and a long-lasting immune response that might reduce the likelihood of HPV progression, the researchers note.1
Seven case-control studies around the world have examined the potential association between non-medicated or copper IUD use and development of endometrial cancer, with six of the seven finding protection against endometrial cancer from the devices, points out David Grimes, MD, author of the chapter on intrauterine contraception in Contraceptive Technology.2 The protective effect was statistically significant in two of those studies.3 The only study that did not find a benefit related to a steel ring used in China, which is not available in Western countries.3
Clinicians will need to be careful in interpretation of claim that IUD use reduces cervical cancer risk, because there might be a selection bias, says Anita Nelson, MD, professor in the Obstetrics and Gynecology Department at the David Geffen School of Medicine at the University of California in Los Angeles. Women at high risk for sexually transmitted diseases (STDs) generally are not given IUDs, Nelson notes. This potential bias in the current study was supported by the fact that the IUD did not protect against cervical cancer in women with HPV infection, she states.
What is the next step in research in examining the protective role of the IUD against cervical cancer? Xavier Castellsagué, MD, MPH, PhD, a researcher at Bellvitge Biomedical Research Institute, L'Hospitalet de Llobregat, Spain, and lead author of the current research, sees two kind of further studies:
- Mechanistic studies to explore and measure the potential local changes in the endometrium as well as in the cervix induced by the device, including local immune markers, hormonal receptors changes, and inflammatory markers, among others.
- Prospective studies recruiting a cohort of IUD users and a matched cohort of non-IUD users measuring HPV and cytological changes every six months to assess HPV incidence, clearance, persistence, and progression to cervical abnormalities and cervical intraepithelial neoplasia 2 (CIN2) in the two cohorts.
"These two study designs would allow to firmly establish whether the protective effect if due to the device or not and explore the underlying mechanisms of such a potential effect," explains Castellsagué.
- Castellsagué X, Díaz 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; 12:1,023-1,031.
- Grimes DA. Intrauterine devices. In: Hatcher RA, Trussell J, Nelson AL, et al. Contraceptive Technology: 19th revised edition. New York: Ardent Media; 2007.
- Grimes DA. Intrauterine device and upper-genital-tract infection. Lancet 2000; 356:1,013-1,019.