The levonorgestrel intrauterine device and ovarian cancer risk: a population-based study

OBJECTIVE: There are widespread changes occurring in contraceptive use, with people moving away from oral contraceptive pills and toward intrauterine devices. Considerable data support the risk reduction for ovarian cancer with oral contraceptive use, but there is little evidence on how levonorgestrel intrauterine device use affects ovarian cancer risk. This paper examines ovarian cancer risk in levonorgestrel intrauterine device users in British Columbia, Canada, between 2002 and 2021. METHODS: This research used population-based data from British Columbia to analyze the risk of ovarian cancer in levonorgestrel intrauterine device users, compared with never users, while controlling for previous oral contraceptive use and age. RESULTS: The final cohort included 788,736 individuals, of whom 52,888 were exposed to the levonorgestrel intrauterine device. Exposed individuals were younger on average and were more likely to have used oral contraceptives. During follow-up, ovarian cancer was diagnosed in 17 exposed individuals and 1184 unexposed individuals. After adjustment for age and oral contraceptive use, levonorgestrel intrauterine device exposure was associated with a reduced risk of ovarian cancer (adjusted hazard ratio 0.57, 95% confidence interval 0.35 to 0.93). In an age-matched 1:1 cohort (n = 105,776), the association was similar but less precise (adjusted hazard ratio 0.61, 95% confidence interval 0.24 to 1.12). In a subgroup restricted to individuals older than 60 years by the end of follow-up (n = 211,866), based on 8 exposed and 720 unexposed ovarian cancer cases, levonorgestrel intrauterine device exposure was not associated with reduced ovarian cancer risk (adjusted hazard ratio 1.59, 95% confidence interval 0.79 to 3.21). CONCLUSIONS: While the findings from the main cohort suggest that use of the levonorgestrel intrauterine device reduced the risk of ovarian cancer, this effect appeared to be confounded by age. These results should be interpreted with caution, as many levonorgestrel intrauterine device users are young and have not reached an age at which they are at a significant risk of ovarian cancer.