Left-Breast Radiation Doubles risk of CAD in Young Women: Study

Radiation therapy (RT) for breast cancer increases the 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.

A team of researchers conducted a study 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. The 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.

The results of the study are as follows:

· 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.

Thus, the researchers concluded that 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.

Reference:

Coronary Artery Disease in Young Women After Radiation Therapy for Breast Cancer: The WECARE Study by Carlson L et. al published in the JACC: CardioOncology.

https://doi.org/10.1016/j.jaccao.2021.07.008