By David Douglas
NEW YORK (Reuters Health) - 18/6/2019
In patients with locally advanced non-small-cell lung cancer undergoing radiotherapy, cardiac radiation exposure is an independent predictor of adverse outcomes, according to a retrospective analysis.
"We found that higher doses of cardiac radiation exposure during lung-cancer radiotherapy are associated with the development of serious cardiac complications such as heart attacks and death," said Dr. Katelyn M. Atkins of the Dana-Farber Cancer Institute and Brigham and Women's Hospital, in Boston.
"Furthermore, patients without a history of prior heart disease were most sensitive to increasing risk of cardiac radiation dose exposure, but the highest absolute risk of serious cardiac complications were seen in patients with a history of heart disease," she told Reuters Health by email.
For their study, online June 10 in the Journal of the American College of Cardiology, Dr. Atkins and colleagues looked at data on 748 patients.
Over a median follow-up of more than 20 months, 77 patients developed at least one major adverse cardiac event (MACE), yielding a two-year cumulative incidence of 5.8%. During this period 533 of the patients died.
The radiation dose delivered to the heart was associated with a significantly increased risk of MACE, with an adjusted hazard ratio of 1.05 per Gy.
In patients without pre-existing coronary heart disease (CHD), compared to a mean heart dose of less than 10 Gy, a greater dose was associated with significantly greater all-cause mortality (HR, 1.34).
This was not the case in CHD-positive patients (HR, 0.94). However, the researchers suggest that this may "reflect an effect of cardiac dose being masked in CHD-positive patients who have elevated baseline cardiac event rates." Overall, there was an increased risk of MACE in CHD-positive versus CHD-negative patients (unadjusted HR, 3.58).
"This study demonstrates the double-edged sword of radiotherapy," senior author Dr. Raymond H. Mak, also of Dana-Farber and Brigham and Women's, told Reuters Health by email. "This cohort of lung-cancer patients was treated with high-dose radiation therapy with a goal of cure, and we historically assumed that cardiac injury from the radiation exposure to the heart would not manifest early enough to impact the survival of these patients who often have a poor prognosis. We are now learning that serious cardiac complications after radiation therapy happen early and more often than we assumed."
"We are hoping studies like this will help educate radiation oncologists to pay closer attention to radiation dose exposure to the heart and to test new radiation-therapy techniques to reduce the risk," he said. "Our next steps are to work with cardiologists to develop methods to reduce the risk of side effects like heart attacks after high-dose radiation for lung-cancer patients."
Dr. Guilherme H. Oliveira of Case Western Reserve University School of Medicine, in Cleveland, Ohio, author of an accompanying editorial, said the study "changes our understanding of this condition by showing that radiation heart disease occurs much earlier than previously thought."
"It also supplies the evidence that was needed to provide these patients with active cardiovascular screening and surveillance by cardio-oncology specialists," he told Reuters Health by email.
J Am Coll Cardiol 2019.