Mediators of Racial Disparities in Heart Dose among Whole Breast Radiotherapy Patients

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Journal of the National Cancer Institute


BACKGROUND: Racial disparities in survival of patients with cancer motivate research to quantify treatment disparities and evaluate multilevel determinants. Prior research has not evaluated cardiac radiation dose in large cohorts of breast cancer patients by race, nor examined potential causes or implications of dose disparities.

METHODS: We used a statewide consortium database to consecutively sample 8,750 women who received whole breast radiotherapy between 2012 and 2018. We generated laterality- and fractionation-specific models of mean heart dose. We generated patient and facility-level models to estimate race-specific cardiac doses. We incorporated our data into models to estimate disparities in ischemic cardiac event development and death. All statistical tests are 2-sided.

RESULTS: Black and Asian race independently predicted higher mean heart dose for most laterality-fractionation groups, with disparities of up to 0.42 Gy for Black and 0.32 Gy for Asian women (left-sided disease and conventional fractionation: 2.13 Gy for Black v. 1.71 Gy for White women, p < .001, two-sided; left-sided disease and accelerated fractionation: Asian 1.59 Gy v. 1.27 Gy for White women, p = .002). Patient clustering within facilities explained 22-30% of the variability in heart dose. The cardiac dose disparities translated to estimated excesses of up to 2.6 cardiac events and 1.3 deaths per 1000 Black and 0.7 cardiac events and 0.3 deaths per 1000 Asian v. White women.

CONCLUSIONS: Depending on laterality and fractionation, Asian and Black women experience higher cardiac doses than White women. This may translate into excess radiation-associated ischemic cardiac events and deaths. Solutions include addressing inequities in baseline cardiac risk factors and facility-level availability and use of radiation technologies.

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ePub ahead of print