Intrauterine devices (IUDs) may protect against cervical cancer. This is the conclusion of the broadest epidemiological study to date in which has participated the research group in Viruses and Cancer of IDIBELL, published at The Lancet Oncology.
The results show that women who use IUD halved the risk of developing cervical cancer compared to those that had never used an IUD. These results are contrary to popular belief that IUD could be a risk factor of cervical cancer. Previous studies on possible effects of IUDs use on the development of this cancer have yielded inconsistent results.
To assess the effects of IUD use on the risk of cervical human papillomavirus (HPV) infection and the risk of developing cervical cancer, Xavier Castellsagué, researcher of Virus and Cancer research group at IDIBELL and of the Cancer Epidemiological Research Program at the Catalan Institute of Oncology (ICO), and colleagues analysed data from ten case-control studies of cervical cancer done in eight countries, and 16 HPV prevalence surveys in women from 4 continents.
Findings were adjusted for confounding factors such as number of Papanicolaou (Pap) smears, number of sexual partners, and age at first intercourse, among others.
Reduces the risk by half
IUD use did not affect the risk of HPV infection, but was associated with a significantly lower risk of cervical cancer for both major cervical cancer types -- reducing the likelihood of developing squamous-cell carcinoma by 44% and adenocarcinoma or adenosquamous carcinoma by 54%.
Interestingly, the length of IUD use did not significantly alter cervical cancer risk. The risk was reduced by nearly half in the first year of use and the protective effect remained significant even after 10 years of use.
The authors say that "the associations found in our study strongly suggest that IUD use does not modify the likelihood of prevalent HPV infection [the cause of cervical cancer], but might affect the likelihood of HPV progression to cervical cancer."
They suggest a number of possible explanations for the protective effect of IUDs including that the process of device insertion or removal may destroy precancerous lesions or that it may induce chronic mucosal inflammation and a long lasting immune response, thereby reducing the likelihood of HPV progression.
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