Modern EBRT reduces CVD risk in breast cancer patients

Advances in external beam radiation therapy (EBRT) techniques in breast cancer treatment have mitigated cardiovascular disease (CVD) risk in women, suggest findings published April 1 in JAMA Network Open. 

Modern photon-based EBRT led to small increases in CVD risk for women with left-sided breast cancer and no differences for most outcomes, wrote a team led by senior author Husam Abdel-Qadir, MD, PhD, from Women’s College Hospital in Toronto, Ontario, Canada.

“These data can help inform shared decision-making conversations with patients about the risks and benefits of radiation therapy, particularly in clinical settings where heart doses are expected to be low,” Abdel-Qadir told AuntMinnie. 

Prior research showed that women with left-sided breast cancer who were treated with EBRT in the ‘70s to early ‘80s had higher rates of CVD mortality compared to women with right-sided breast cancer. 

Since then, radiotherapy delivery has undergone several improvements to reduce mean heart doses. These include replacing 2D radiation therapy with photon-based 3D conformal and intensity modulated radiation therapy. Improvements such as deep inspiration breath hold, CT simulation, dose evaluation, and planning software have also helped to reduce mean heart doses from left-sided breast radiation. 

Abdel-Qadir and colleagues noted that contemporary population-level data on long-term CVD risk are limited. The researchers added to the literature by studying links between contemporary left-sided EBRT and CVD risk among breast cancer patients. 

The population-based, retrospective cohort study included data from 76,586 women with an average age of 59 years. Of these, 38,427 had left-sided breast tumors. The total cohort underwent follow-up appointments for a median of 10.9 years. The women received EBRT between 2002 and 2017 and were followed up through 2025 for most outcomes and through 2022 for cause-specific mortality. 

The 15-year cumulative incidence of first-CVD hospitalization did not significantly differ by laterality, though new cardiac diagnoses in women with preexisting CVD were more frequent after left-sided EBRT. 

Finally, the team observed no differences in all-cause mortality or recurrent CVD hospitalizations among women with pre-existing CVD. 

Abdel-Qadir said the differences in new cardiac diagnoses and hospitalization are small in absolute terms on the population level. 

“However we have to remember for each of these women, it was a meaningful and real issue,” he told AuntMinnie. 

Abdel-Qadir also said the findings provide reassurance than modern photon-based EBRT techniques “have largely reduced” the excess long-term cardiovascular risk historically associated with left-sided breast radiation.  

“This is relevant to the ongoing discussion about proton beam therapy. This new radiation modality can further reduce cardiac radiation exposure but is more expensive and less widely available,” he said. “Our data will inform discussions about how it should be best allocated to reduce cardiovascular risk for women receiving left-sided breast radiation.” 

The findings may help in transitioning from laterality to dosimetry-informed risk models for personalized decisions, according to an accompanying editorial by Avirup Guha, MD, from Augusta University in Georgia. 

Guha added radiotherapy exposure should be considered one part of an integrated cardiovascular prevention plan and “not as a standalone risk label.” 

“Cardio-oncology guidance emphasizes baseline risk assessment, targeted surveillance, and aggressive management of modifiable risk factors tailored to treatment exposures and vulnerability,” Guha wrote. “For many survivors, the highest-yield intervention is systematic prevention: blood pressure and lipid control, diabetes optimization, smoking cessation, and physical activity.” 

Read the full study here.