In a combined analysis of several previous studies, women who used intrauterine devices (IUDs) had a 45% reduction in risk of cervical cancer. These results were published in Lancet Oncology.
The most important cause of cervical cancer is infection with a high-risk type of human papillomavirus (HPV). Human papillomaviruses consist of a group of more than 100 different viruses. Some types of HPV cause warts on the hands or feet; others cause genital warts; and some have been linked with cancer, most notably cervical cancer. The types of HPV most commonly linked with cervical cancer are HPV16 and HPV18, but several other high-risk types contribute to cancer as well.
The types of HPV that cause cervical cancer or genital warts are transmitted sexually. HPV infection is extremely common and generally occurs soon after an individual becomes sexually active. Although most infections resolve on their own, some persist and can lead to precancerous or cancerous changes to the cervix, vulva, vagina, penis, and anus. Persistent infections appear to pose the greatest cancer threat. Vaccines that prevent infection with HPV16 and HPV18 are likely to substantially reduce the occurrence of HPV-related cancers.
Among women who have not been vaccinated against HPV, researchers continue to explore factors that affect the likelihood of cervical cancer. Use of IUDs has been reported to reduce the risk of endometrial (uterine) cancer, but it’s been uncertain whether and how IUD use affects risk of cervical cancer.
To explore the relationship between IUD use and cervical cancer risk, researchers in Spain combined information from 26 previous studies.
The results indicated that although IUD use did not affect the likelihood of having an HPV infection, women who used IUDs had a substantially reduced risk of developing cervical cancer. IUD users had a 44% reduction in risk of squamous cell carcinoma of the cervix and 54% reduction in risk of adenocarcinoma and adenosquamous carcinoma of the cervix. The reduction in risk was similar regardless of how long the IUD was used.
The reasons for the lower risk of cervical cancer among IUD users are uncertain, but the researchers provide a few possible explanations. For example, IUDs may prompt a chronic, low-grade inflammatory response that alters the course of HPV infections. The process of inserting or removing IUDs may also affect immune responses in the cervix or eliminate some small precancers.
The results of this study should be reassuring to women who use IUDs. IUDs do not appear to increase the risk of cervical cancer and may, in fact, reduce cancer risk.
Reference: Castellsague X, Diaz M, Vaccarella S et al. Intrauterine device use, cervical infection with human papillomavirus, and risk of cervical cancer: a pooled analysis of 26 epidemiologic studies. Lancet Oncology. Early online publication September 13, 2011.