Abstract P450: Radon is Associated With Clonal Hematopoiesis of Indeterminate Potential in the Women’s Health Initiative

Abstract

Background: Clonal hematopoiesis of indeterminate potential (CHIP) occurs when there is expansion of leukocyte clones in the blood due to mutations in hematopoietic stem cells. CHIP is associated with a high risk of hematologic malignancy and increased risk of cardiovascular disease (CVD). Although the environmental risk factors for CHIP remain poorly understood, radon is a ubiquitous mutagen and may deliver non-negligible doses of α-radiation to bone marrow that trigger CHIP development. Methods: We conducted a cross-sectional study of 10,495 postmenopausal women without hematologic malignancy from the Women’s Health Initiative clinical trials and observational study (mean age: 69 years; 82% white; 9% African American; 4% Hispanic/Latina; 3% Asian). Using blood from the 1993-1998 screening visit or a subsequent annual visit, and whole genome sequence data from the Trans-Omics for Precision Medicine project, we identified CHIP using the GATK Mu TECT2 somatic variant caller, a pre-specified list of leukemogenic driver mutations in 74 genes, and a threshold variant allele fraction > 0.02. We linked geocoded participant addresses at the time of blood draw to county-level, indoor, screening radon concentrations that were predicted by the Environmental Protection Agency (EPA) in 1993 using data on indoor radon, geology, aerial radioactivity, soil parameters, and foundation types. Radon exposure was classified as follows: Zone 3 (< 2 pCi/L), Zone 2 (2-4 pCi/L), and Zone 1 (> 4 pCi/L), the level at which EPA recommends remediation. We estimated the radon-related risk of CHIP as an odds ratio (OR, 95% CI) using logistic regression with and without adjustment for study design, participant sampling, age, race/ethnicity, smoking, and other sociodemographic / behavioral covariates. Results: We identified CHIP in 887 (8.5% of) participants. 3106 (29.6%), 3982 (37.9%), and 3407 (32.5%) had Zone 3, 2, and 1 radon exposures. The corresponding percentage of participants with CHIP across zones was 7.6%, 8.6%, and 9.1%. Relative to participants in Zone 3, those in Zones 2 and 1 had a higher adjusted risk of CHIP: OR (95% CI) = 1.13 (0.95, 1.35) and 1.24 (1.03, 1.48). Conclusion: Risk of CHIP was positively associated with indoor radon concentrations in this cross-sectional study of post-menopausal women. Longitudinal study of temporally integrated, in-home radon exposures, incident CHIP, and CVD would help confirm this novel radon-CHIP association and place it in context.