Disparities in Radiation Exposure to the Heart from Whole-Breast Radiation Therapy

The intersection of disease biology with certain social determinants of health can lead to inferior outcomes, but there are other factors that influence disparities in care and outcome. To understand mediators of racial disparities among women with early-stage breast cancer receiving adjuvant whole-breast radiation therapy (WBRT), researchers obtained RT dosimetry data from the Michigan Radiation Oncology Quality Consortium (MROQC) database.

Mean heart dose (MHD) was compared for Asian, Black, and white women who were treated with WBRT at 25 institutions between 2012 and 2014. Of 8750 patients in the analysis, 2% were Asian, 18% Black, and 80% white. Black race was independently associated with higher MHD for women with left-sided cancers receiving conventional fractionation (MHD, 2.13 Gy for Black women vs. 1.71 Gy for white women). Asian women with left-sided cancers receiving an accelerated fractionation schedule also had higher MHD (1.59 Gy vs. 1.27 Gy for white women).

Black patients were much more likely than Asian or white patients to receive intensity modulated radiation therapy, which has been associated with greater MHD.

Based on modeling, higher cardiac dose would increase the number of events and deaths in Black and Asian patients compared with white patients, with an excess of 2.6 events and 1.3 deaths per 1000 Black patients and 0.7 events and 0.3 deaths per 1000 Asian patients.