EXECUTIVE SUMMARY

Results of a just-published systematic review indicate that in women who used an intrauterine device, the incidence of cervical cancer was one-third lower.

  • The findings suggest that women who used an intrauterine device (IUD) experienced less cervical cancer (summary odds ratio 0.64, 95% confidence interval, 0.53-0.77). Neither confounding by recognized risk factors nor publication bias seems to be a plausible explanation for the apparent protective effect, researchers note.
  • The analysis is the first to combine data from multiple studies on IUDs and cervical cancer, and it includes data from 16 observational studies involving more than 12,000 women worldwide.

Results of a just-published systematic review indicate that in women who used an intrauterine device (IUD), the incidence of cervical cancer was one-third lower.1 The analysis is the first to combine data from multiple studies on IUDs and cervical cancer, and it includes data from 16 observational studies involving more than 12,000 women worldwide.

Researchers at the University of Southern California identified studies with individual-level measures of use of an IUD and incident cervical cancer. They extracted point and interval estimates of the association between use of an IUD and incident cervical cancer to develop a structured database, then implemented a random-effects meta-analysis to synthesize extracted estimates and assess likely influence of publication bias, residual confounding, heterogeneity of true effect size, and human papillomavirus prevalence and cervical cancer incidence. The findings suggest that women who used an IUD experienced less cervical cancer (summary odds ratio 0.64, 95% confidence interval, 0.53-0.77). Neither confounding by recognized risk factors nor publication bias seems to be a plausible explanation for the apparent protective effect, researchers note.1

Victoria Cortessis, PhD, lead author and associate professor of clinical preventive medicine at the Keck School of Medicine at the university, terms the pattern “stunning.”

“The possibility that a woman could experience
some help with cancer control at the same time she is making contraception decisions could potentially be very, very impactful,” noted Cortessis in a press statement.

Check Previous Data

Results of a 2011 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, showed similar protective effects.2 In that analysis, use of an IUD lowered the risk of cervical cancer by 45%, compared with never using an IUD. The researchers noted that the protective effect was seen in the first year of IUD use and continued for up to 10 years.

In the 2011 analysis, researchers pulled data from 10 case-control studies of cervical cancer done in eight countries and information from 16 human papillomavirus (HPV) prevalence surveys of women 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 were included from the HPV survey.2

The 2011 analysis indicates the chances of developing squamous-cell carcinoma were reduced by 44%, and the risk for adenocarcinoma or adenosquamous carcinoma was lowered by 54%. Although the data in the study 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.2

More Research Needed

Scientists suggest the process of inserting or removing the device might destroy precancerous lesions. IUD use also might induce chronic mucosal inflammation and a long-lasting immune response that might decrease the likelihood of HPV progression, researchers note.2 Seven case-control studies around the world have examined the potential association between non-medicated or copper IUD use and the development of endometrial cancer, with six of the seven studies finding protection against endometrial cancer from the devices, noted David Grimes, MD, author of the chapter on intrauterine contraception in the 19th revised edition of Contraceptive Technology.3 The protective effect was statistically significant in two of the studies.4 Two studies have addressed cervical cancer, noted Grimes; both found a 40% reduction in risk associated with IUD use, which was not statistically significant.3

“If we can demonstrate that the body mounts an immune response to having an IUD placed, for example, then we could begin investigating whether an IUD can clear a persistent HPV infection in a clinical trial,” commented coauthor Laila Muderspach, MD, chair of obstetrics and gynecology at the Keck School of Medicine, in a press statement.

According to 2017 estimates from the Atlanta-based American Cancer Society, about 12,820 new cases of invasive cervical cancer will be diagnosed, while some 4,210 women will die from cervical cancer.5 Although cervical cancer was once one of the most common causes of cancer death in U.S. women, the cervical cancer death rate has gone down by more than 50% during the past 40 years. The increased use of the Pap test, which can identify changes in the cervix before cancer develops, is the primary reason for the change in the cervical cancer death rate.5

Global statistics paint a sobering picture. According to the World Health Organization, about 528,000 women were diagnosed with cervical cancer worldwide in 2012, and 266,000 women died from the disease.6

In developing countries with rapidly-increasing populations and scarce cancer prevention resources, such as the HPV vaccine and regular cervical screenings, a contraceptive that offers protection against cervical cancer could have a “profound” effect, says Cortessis. Many women in the developing world are about to enter the age range where the risk for cervical cancer is the highest, she notes.

“Even if the rate of cervical cancer remains steady, the actual number of women with cervical cancer is poised to explode,” Cortessis said in the release. “IUDs could be a tool to combat this impending epidemic.”

REFERENCES

  1. Cortessis VK, Barrett M, Brown Wade N, et al. Intrauterine device use and cervical cancer risk: A systematic review and meta-analysis. Obstet Gynecol 2017; doi: 10.1097/AOG.0000000000002307.
  2. 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;12:1023-1031.
  3. Grimes DA. Intrauterine devices. In: Hatcher RA, Trussell J, Nelson AL, et al. Contraceptive Technology, 19th revised edition. New York: Ardent Media; 2007.
  4. Grimes DA. Intrauterine device and upper-genital-tract infection. Lancet 2000;356:1013-1019.
  5. American Cancer Society. What Are the Key Statistics About Cervical Cancer? Available at: http://bit.ly/2kUcifg. Accessed Nov. 20, 2017.
  6. World Health Organization (WHO). Comprehensive Cervical Cancer Control. A Guide to Essential Practice. Second edition. WHO; 2014.