Women who use intrauterine devices may not just be preventing pregnancy but may also be protecting themselves from cervical cancer, according to a new study involving more than 20,000 women in different countries that was published in The Lancet Oncology today.

Contradicting the popular view that IUDs increase cancer risk, Xavier Castellsagué, a virus and cancer researcher at the Institut d’Investigacio Biomedica de Bellvitge (IDIBELL) in Barcelona, Spain, and colleagues found that women who used IUDs had half the risk of developing cervical cancer compared to women who had never used one.

There is evidence that IUDs seem to protect against cancer of the lining of the uterus, write the researchers, but previous studies have generally been inconsistent about the effect on cervical cancer risk.

For their study, the researchers assessed whether using IUDs affected cervical human papillomavirus (HPV) infection and the risk of developing cervical cancer.

They pooled data from ten case-control studies of cervical cancer conducted in eight countries (covering 2,205 women with cervical cancer and 2,214 matched controls without cervical cancer), and 16 HPV prevalence surveys of 15,272 healthy women in 14 countries. Information on IUD use came from personal interviews.

The researchers adjusted the findings for other potential influencing factors such as number of Pap smear tests, number of sexual partners and age at first intercourse.

Their analysis showed that:

  • IUD use did not affect the risk of HPV infection, but was linked to a significantly lower risk of cervical cancer for both major types of cervical cancer: squamous-cell carcinoma (risk reduced by 44%) and adenocarcinoma or adenosquamous carcinoma (risk reduced by 54%).

  • Duration of IUD use did not alter cervical cancer risk significantly.

  • The risk was nearly halved within the first year of use, and this protective effect remained significant even after 10 years of use.

The researchers concluded their findings by suggesting that while IUD use does not appear to change the likelihood of becoming infected with HPV, it does appear to reduce the odds of such an infection progressing to the cervical cancer stage.

While they did not investigate the cause of this effect, the researchers suggested a reason could be the procedure of inserting or removing an IUD could destroy pre-cancerous lesions, or cause a chronic inflammation which produces a long-lasting cellular immune response which in turn reduces the odds of HPV progression.

Written by Catharine Paddock PhD