Does IUD type impact cervical cancer risk?

New research published in Obstetrics & Gynecology indicates that risk of high-grade cervical neoplasms is lower with copper (Cu) intrauterine devices (IUDs) than with the levonorgestrel-releasing intrauterine system (LNG-IUS).  More than 100 million women worldwide use IUDs as contraception so these findings could have global implications.

Methods
The current study was a retrospective cohort analysis of 10,674 patients who received IUDs at Columbia University Medical Center. The authors restricted their cohorts to women age 45 years or younger at time of IUD insertion. Patients with a history of endometrial or cervical neoplasms or who had a prior IUD placement were excluded. 

By default, women were in the Cu IUD cohort unless documentation of LNG-IUS appeared in the database. The outcome of the study was high-grade malignant cervical neoplasm or cervical neoplasm with a high association with malignancy, such as cervical intraepithelial neoplasia (CIN) grade II or III. Cervical polyps, CIN grade I, and metastatic spread of neoplasm to the cervix were excluded. Patients in the cohort and their outcomes were identified by a combination of procedure codes, condition codes, and medication exposures in billing and claim data. The authors adjusted for confounding with propensity score stratification and 1:1 matching.

Finings
A total of 10,674 patients were studied. Of them, 8,274 patients were in the Cu IUD cohort and 2,400 were in the LNG-IUS cohort. Ninety-seven percent (2,332) of the LNG-IUS users received a 52-mg device. Median age was 29 years (range 24-35) years in the Cu IUD cohort and 28 years (23-34) in the LNG-IUS cohort. During follow-up, 1,820 (22.0%) Cu IUD users and 797 (33.2%) of LNG-IUS users had a documented IUD removal procedure. 

Before propensity score adjustment, the authors identified 114 cases of cervical neoplasm: 77 (0.9%) in the Cu IUD cohort and 37 (1.5%) in the LNG-IUS cohort. Propensity score matching analysis identified 7,114 Cu IUD and 2,174 LNG-IUS users, with covariate balance achieved over 16,827 covariates. 

Of the women with Cu IUDs, 0.7% were diagnosed with high-grade cervical neoplasia versus 1.8% in the LNG-IUS cohort (IR 2.4 [95% CI 1.9-2.9] cases/1000 person years and IR 5.2 [95% CI 3.7-7.1] cases/1000 person years, respectively). Relative risk for high-grade cervical neoplasms among Cu IUD users was 0.38 (95% CI 0.16-0.78, P< .02) compared with LNG-IUS users. 

Conclusions
The authors noted that the association between IUD usage and high-grade cervical neoplasm incidence has implications for public health on a global scale becuase more than 100 million women worldwide use the devices for contraception. The approximate 1% difference in high-grade cervical neoplasm incidence between Cu IUD and LNG-IUS user could have a large effect, especially in areas with the highest incidence of cervical cancer.