Preeclampsia and Site-Specific Cancer Risk: A Nationwide Population-Based Study

Background: Preeclampsia, a condition of high blood pressure during pregnancy, is linked to microangiopathy in various organs and may contribute to cancer development. This study aimed to evaluate cancer risk in women with newly diagnosed preeclampsia. Methods: We conducted a nationwide, population-based retrospective study using data from the Korean National Health Insurance claims database (2008-2020). Women diagnosed with preeclampsia between 2009 and 2013 were compared to a control group who underwent appendectomy but did not have preeclampsia. Participants with a prior cancer diagnosis were excluded. Cancer occurrence was assessed using the International Classification of Diseases, 10th revision codes. Results: Data from 42,380 preeclampsia patients and 105,327 controls were analyzed. Cancer incidence rates were 333.1 per 100,000 person-years in the preeclampsia group and 377.0 in controls. Preeclampsia was associated with significantly higher risks of gallbladder and biliary tract cancers (HR 5.49, 95% CI 1.23-24.50), breast cancer (HR 1.17, 95% CI 1.02-1.34), and thyroid cancer (HR 1.21, 95% CI 1.10-1.34). However, it was linked to lower risks of ovarian cancer (HR 0.44, 95% CI 0.27-0.74) and leukemia (HR 0.36, 95% CI 0.16-0.81). All hazard ratios were adjusted for age, which differed substantially between the two groups; unadjusted incidence rates and age-adjusted hazard ratios therefore differed in direction for some sites. Conclusions: Preeclampsia was associated with an increased risk of certain cancers, including breast and thyroid cancers, and with a decreased risk of ovarian cancer and leukemia. Because the control group was older than the preeclampsia group, crude incidence rates and age-adjusted hazard ratios differed in direction; the age-adjusted estimates should therefore be regarded as the primary findings. Several site-specific associations, particularly those based on small event counts (e.g., gallbladder and biliary tract cancer), should be interpreted as exploratory and warrant replication.