Cardiac-Exposure Limits in Lung Cancer Radiotherapy Help Curb Side Effects

By David Douglas

December 28, 2020

NEW YORK (Reuters Health) - In patients with non-small-cell lung cancer, left anterior descending (LAD) coronary-artery radiation exposure is associated with major adverse cardiac events (MACE) and all-cause mortality, according to a new analysis.

"This study builds on the prior work from our group and others that have demonstrated the importance of reducing cardiac-radiation dose exposure in patients with lung cancer treated with radiation therapy, to reduce mortality and risk of major cardiac side effects," said Dr. Raymond H. Mak of the Dana-Farber Cancer Institute, Brigham and Women's Hospital, in Boston.

"The unique aspects of this study," he told Reuters Health by email, "include a more refined analysis of the risk for major adverse cardiovascular events (such as heart attacks) that factors in both radiation-dose exposure to specific portions of the heart such as the coronary arteries and the patient's baseline cardiac condition."

Dr. Mak and colleagues studied 701 patients with locally advanced lung cancer with a median age of 65 years who were treated with thoracic radiotherapy between 2003 and 2017. Median follow-up was for 20.4 months, the team reports in JAMA Oncology.

Following adjustment for baseline coronary heart disease (CHD) and other factors, a LAD coronary artery V15 Gy of 10% or more was associated with increased risk of MACE (adjusted hazard ratio, 13.90; P=0.03), This was also true of all-cause mortality (aHR, 1.58; P=0.02).

In patients without CHD, associations with increased one-year MACE were also seen after LAD-coronary-artery radiation exposure as well as for other levels of exposure in the circumflex coronary artery and other sites, including the left ventricle with a V15 Gy greater than or equal to 1%.

In patients with CHD, only the latter finding additionally increased the risk of MACE.

This suggests that optimal cardiac-dose constraints may differ based on pre-existing CHD, said Dr. Mak. "These insights will allow our field to continue to transform the way we approach radiation treatment planning, which has been previously been focused on minimizing radiation exposure to the lungs and considering the heart only secondarily and in an overly simplified fashion."

He concluded, "The trade-offs of trying to deliver sufficient radiation dose to the cancer to achieve a cure, while not severely damaging the heart and lungs, are extremely challenging. We hope that our study will provide radiation oncologists with insights into how to minimize the risk of major cardiac complications by focusing their efforts on personalizing radiation plans to reduce the dose exposure to the left coronary arteries."

Dr. Sherry-Ann Brown, co-author of an accompanying editorial, told Reuters Health by email, "We need innovative ways to be able to predict outcomes in individuals treated with radiation therapy for cancer. As cardiologists, our ultimate goal is to protect the hearts of cancer patients and survivors."

"Findings from studies like these give us additional insights that we can potentially apply to predict and prevent poor outcomes," said Dr. Brown, of the Medical College of Wisconsin, in Milwaukee.

SOURCE: and JAMA Oncology, online December 17, 2020.