Key result
Left-sided breast cancer radiation is linked to ~150% higher CAD risk versus right-sided therapy.
Why the study?
Radiation therapy for breast cancer increases CAD risk, with left-sided treatment conferring greater cardiac exposure, but radiation-associated CAD risk specifically in younger survivors is not well defined.
Does left-sided radiation therapy increase the risk of incident coronary artery disease compared to right-sided radiation therapy in women diagnosed with breast cancer before age 55?
Cohort (n=972)
Yes
Does left-sided radiation therapy increase the risk of incident coronary artery disease compared to right-sided radiation therapy in women diagnosed with breast cancer before age 55?
Hazard Ratio: 2.5 (95% CI 1.3–4.7)
Absolute Event Rate: 10.5% vs 5.8%
p-value: p=0.010
Left-sided radiation therapy for breast cancer in young women (<55 years) is independently associated with a more than twofold increased risk of developing coronary artery disease compared to right-sided radiation therapy.
Supports minimizing cardiac radiation exposure during left-sided RT in young women; extends observational data but remains hypothesis-generating.
Radiation therapy (RT) for breast cancer increases risk of coronary artery disease (CAD). Women treated for left- vs right-sided breast cancer receive greater heart radiation exposure, which may further increase this risk. The risk of radiation-associated CAD specifically among younger breast cancer survivors is not well defined. The purpose of this study was to report CAD risk among participants in the Women’s Environmental Cancer and Radiation Epidemiology Study. A total of 1,583 women who were <55 years of age when diagnosed with breast cancer between 1985 and 2008 completed a cardiovascular health questionnaire. Risk of radiation-associated CAD was evaluated by comparing women treated with left-sided RT with women treated with right-sided RT using multivariable Cox proportional hazards models. Effect modification by treatment and cardiovascular risk factors was examined. In total, 517 women who did not receive RT and 94 women who had a pre-existing cardiovascular disease diagnosis were excluded, leaving 972 women eligible for analysis. Their median follow-up time was 14 years (range 1-29 years). The 27.5-year cumulative incidences of CAD for women receiving left- vs right-sided RT were 10.5% and 5.8%, respectively (P = 0.010). The corresponding HR of CAD for left- vs right-sided RT in the multivariable Cox model was 2.5 (95% CI: 1.3-4.7). There was no statistically significant effect modification by any factor evaluated. Young women treated with RT for left-sided breast cancer had over twice the risk of CAD compared with women treated with RT for right-sided breast cancer. Laterality of RT is independently associated with an increased risk of CAD and should be considered in survivorship care of younger breast cancer patients.
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Carlson et al. (2021) conducted a cohort in Breast cancer (n=972). Left-sided radiation therapy vs. Right-sided radiation therapy was evaluated on Incident coronary artery disease (CAD) (HR 2.5, 95% CI 1.3-4.7, p=0.010). Young women treated with radiation therapy for left-sided breast cancer had over twice the risk of coronary artery disease compared with women treated with right-sided radiation therapy (HR 2.5).
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