Do IUDs Prevent Cervical Cancer?

Meta-analysis suggests that IUDs decrease risk for cervical cancer

IUD
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Of course, intrauterine devices (IUDs) are remarkably effective at preventing pregnancy. During the first year of use, IUDs fail in less than 1 percent of women using them.

In addition to preventing pregnancy, new research shows that IUDs may also help prevent cervical cancer—particularly among lower-income populations where less than 2 percent of women are vaccinated against the human papillomavirus (HPV).

Although not all women with HPV develop cervical cancer, HPV is the primary cause of cervical cancer.

Research

In a December 2017 systematic review and meta-analysis titled Intrauterine Device Use and Cervical Cancer Risk, Cortessis and colleagues identified 16 high-quality studies for inclusion in their analysis. Data pooled from these studies represented 12,482 women: 4945 women with cervical cancer and 7537 without cancer.

After controlling for confounding variables like HPV prevalence and cervical cancer incidence in source populations, the researchers found that cervical cancer was nearly a third less common in women using IUDs.

How Do IUDs Work?

The vagina is connected to the uterus by the cervix, a necklike passage. Using a speculum, a physician will position an IUD for placement into the uterus. The IUD is then placed into the uterus using a special inserter, and held in place by the cervical os.

According to the authors of Current Medical Diagnosis & Treatment 2018, here is the timing of IUD placement:

Insertion can be performed during or after the menses, at midcycle to prevent implantation, or later in the cycle if the patient has not become pregnant. There is growing evidence to suggest that IUDs can be safely inserted in the immediate postabortal and postpartum periods.

Copper IUDs work by inducing a sterile inflammatory reaction that causes the body to kill the sperm. The copper is recognized as a foreign body which the body will attack via the immune system.

The hormonal IUD Progestasert works by releasing hormones that have a spermicidal effect.

The hormonal IUD Mirena has the following actions:

  • Thickening cervical mucus to prevent sperm from entering the uterus
  • Inhibiting sperm from reaching or fertilizing the egg
  • Thinning the lining of the uterus

Historically, IUDs have been linked to pelvic inflammation and infertility; however, new devices are much safer. In addition to being highly effective, modern IUDs also have few negative side effects.

Women at high risk for either being infected with a sexually transmitted infection or developing bacterial endocarditis should not use IUDs. Furthermore, in women with uterine fibroids, IUDs may not be effective because they alter the shape of the uterine cavity.

In the United States, IUDs are drastically underutilized. Only 1 percent of American women use IUDs. In Europe and Canada, between 15 percent and 30 percent of women use IUDs.

How Do IUDs Prevent Cervical Cancer?

It’s unclear how exactly IUDs prevent cervical cancer.

Nevertheless, there are a few different hypotheses.

The placement of the IUD may induce the immune system to target HPV infections and preinvasive (cancerous) lesions. Specifically, IUDs are placed over the transformation zone and focus the immune response on the transformation zone. The transformation zone is an area of the cervix with high cell turnover and the most common place for cervical cancer to develop.

Research findings that support this first hypothesis are that cervical lesions progress more quickly in women who are immunocompromised. Moreover, researchers have found that patients who have cervical lesions removed fare better if the tissue containing these lesions contains CD4+ T-cells and CD11c+ dendritic cells.

The presence of these cells, which are types of lymphocytes active in immune responses, indicate immune infiltration.

Alternatively, a more long-term immune response has been suggested to explain the protective effect of IUDs. According to Cortessis and co-authors:

"Mechanisms involving more chronic response to the presence of an IUD have also been suggested …. IUDs may affect HPV persistence through ‘changes in local mucosal immune status’ caused by chronic, low-grade inflammation in the endocervix and cervix or by induction of ‘local small foci of chronic inflammation’ resulting from IUD insertion or removal and subsequent long-lasting immune reaction."

In other words, over time, low-grade inflammation secondary to the presence of the IUD could bolster immune potential of the mucosa of the cervix. Or, small islands of chronic inflammation could induce a beneficial immune response after IUD insertion or removal, resulting in a long-term immune reaction.

Finally, although unlikely, it’s possible that when the IUD is either inserted or removed, it may scrape off cancerous cells.

Implications

It’s premature to take the results of this study and suggest that women get IUDs to prevent cervical cancer. Intrauterine devices do have their benefits—including high efficacy and few adverse effects—but as for now, we need to do more research to bolster this study's findings and figure out how and which types of IUDs can prevent cervical cancer.

Although most of the women in this study were using non-hormonal IUDs, the researchers didn’t have enough information to compare the protective effects of copper IUDs versus hormonal IUDs. Furthermore, other factors could also play a role in potential protective effects, including duration of use or age at placement. Such factors would need to be more thoroughly examined to inform clinical guidelines.

Another limitation of this meta-analysis could lie in the heterogeneity of the individual studies themselves. The researchers don’t question the design of own their meta-analysis or the veracity of their results. Specifically, they don’t ascribe the suggested protective effects of IUDs to things like study design, publication bias, or residual confounding by cervical cancer risk and protective factors.

A meta-analysis, however, is only as good as its component studies, and because this study was observational and retrospective—with the researchers looking back at work done by others—it’s possible that the individual studies were fundamentally flawed. For instance, the authors of the 16 studies examined could have inconsistently or inadequately considered differences in risk or protective factors such as access to preventive care or effects of socioeconomic status.

Despite it being too early to determine how to incorporate the results of this study into clinical practice, the researchers do foresee great benefit of this research—especially among those at highest risk for cervical cancer: lower income populations with limited access to screening and high frequency of cervical cancer. These populations extend far beyond the United States and include those in the developing world.

The researchers conclude their study with the following:

"If such efforts substantiate a preventive influence of the IUD, future contraceptive counseling may routinely incorporate this potential noncontraceptive benefit of the IUD. Translational potential of this avenue of research is underscored by the great and growing need for approaches to cervical cancer prevention that can be widely used by HPV-exposed women in low-resource settings, frequent need for contraception among these women, and credible documentation of other noncontraceptive benefits of IUDs."

More Information About Cervical Cancer

Cervical cancer is the most common gynecological cancer, and the third most common type of cancer worldwide. The International Agency for Research on Cancer estimates that by 2030 worldwide there will 710,000 cases of cervical cancer and 383,000 cervical cancer deaths annually.

The primary risk factor for cervical cancer is HPV, but there are other risk factors, too including the following:

  • Obesity
  • Smoking
  • Lower educational attainment
  • Older age
  • Number of pregnancies
  • Poverty
  • Combination oral contraceptives
  • Having several sexual partners during the course of a lifetime
  • Immunosuppression

Because women with early stages of cervical cancer often present without symptoms, the only way that a physician can identify the disease is by Pap tests and HPV screening. Furthermore, diagnosis of cervical cancer often requires a biopsy of the cervix, which is called a colposcopy. Importantly, risk factors like poverty and lower educational attainment don’t mediate the progression of cervical cancer per se, but rather decrease the chances that a woman will be screened.

In general, early stage disease is highly treatable with surgical removal of the cancerous lesions. Treatment of advanced disease is less successful and requires chemoradiation.

The five-year survival rate is the percentage of women alive five years after diagnosis. According to the American Society of Clinical Oncology:

"When detected at an early stage, the 5-year survival rate for women with invasive cervical cancer is 91%. About 46% of women with cervical cancer are diagnosed at an early stage. If cervical cancer has spread to surrounding tissues or organs and/or the regional lymph nodes, the 5-year survival rate is 57%. If the cancer has spread to a distant part of the body, the 5-year survival rate is 17%."

Overall, the combination of HPV vaccine and clinical screening provide the best protection against cervical cancer.

As stated in Shwartz’s Principles of Surgery:

"Several randomized clinical trials involving approximately 35,000 young women have shown that both Gardasil and Cervarix [two HPV vaccines] prevent nearly 100% of the HPV subtype-specific precancerous cervical cell changes for up to 4 years after vaccination among women who were not infected at the time of vaccination; vaccination occurred before sexual debut …. Vaccination has not yet been shown to protect women who are already infected with HPV-16 or HPV-18 at the time of vaccination."

A Word From Verywell

Recent research suggests that placement of an IUD decreases the risk of cervical cancer. However, more research needs to be done to support these findings and figure out why and what types of IUDs confer protection. For now, you should view IUDs for what they are—highly effective and safe means of birth control. The potential for IUDs to prevent cervical cancer should be viewed as a potential bonus.

Sources:

Cortessis VK et al. Intrauterine Device Use and Cervical Cancer Risk: A Systematic Review and Meta-analysis. Obstetrics & Gynecology. 2017. [epub ahead of print]

Hall JE. Infertility and Contraception. In: Kasper D, Fauci A, Hauser S, Longo D, Jameson J, Loscalzo J. eds. Harrison's Principles of Internal Medicine, 19e New York, NY: McGraw-Hill; 2014.

Hamilton C, Stany M, Gregory W, Kohn EC. Gynecology. In: Brunicardi F, Andersen DK, Billiar TR, Dunn DL, Hunter JG, Matthews JB, Pollock RE. eds. Schwartz's Principles of Surgery, 10e New York, NY: McGraw-Hill; 2015.

Woo J. Gynecologic Disorders. In: Papadakis MA, McPhee SJ, Rabow MW. eds. Current Medical Diagnosis & Treatment 2018 New York, NY: McGraw-Hill.