Low-dose aspirin use and risk of ovarian cancer: a combined analysis from two nationwide studies in Denmark and Sweden.

BackgroundStudies on association between low-dose aspirin use and ovarian cancer risk were mostly based on self-reported medication use and few had large enough sample size to investigate the potential modification effect by ovarian cancer risk factors.MethodsIn these two nationwide nested case-control studies among the Danish and Swedish female population, 11,874 women with ovarian cancer (30-84 years old) (Denmark: 7328 diagnosed in 2000-2019, Sweden: 4546 diagnosed in 2010-2018) were randomly age- matched with 473,960 female controls (293,120 from Denmark, and 181,840 from Sweden). We used conditional logistic regression to estimate odds ratios (OR) and 95% confidence intervals (CI) and combined the estimates based the fixed-effect assumption. Effect modification by inflammation-related risk factors and by indication (cardiovascular disease, CVD) were also investigated.ResultsEver use of low-dose aspirin was not strongly associated with the overall risk of ovarian cancer (OR = 0.97; 95%CI: 0.92-1.03). However, the association differed according to parity (nulliparous: OR = 0.80, 95%CI: 0.70-0.92; parous: OR = 1.00, 95%CI: 0.94-1.07; p-interaction = 0.0024), and according to history of CVD (no CVD: OR = 0.91, 95%CI: 0.82-1.00; ever CVD: OR = 1.05, 95%CI: 0.97-1.13; p-interaction =0.0204).ConclusionsLow-dose aspirin use was associated with a decreased ovarian cancer risk especially in nulliparous women and in women without CVD diagnosis.