Radiotherapy more likely to cause cardiotoxicity among lung cancer patients

A significant number of patients—most with no history of cardiac conditions—developed cardiac toxicity secondary to radical radiotherapy (RRT) for lung cancer, according to the results of an abstract presented at the European Lung Cancer Congress 2019, held in Geneva, Switzerland, April 10-13.

“In comparison to previous findings, where cardiac events happen much longer after thoracic radiotherapy…after lung-cancer radiotherapy, we’ve seen a much sooner onset of cardiac events after radiotherapy—so probably in the first year or two…And this is very significant because a lot of them are ischemic events [which affect] survival outcomes,” said lead author Fei Sun, MD, PhD, Oncology, The Leeds Teaching Hospital NHS Trust St. James University Hospital, Leeds, United Kingdom, in an interview with ecancer.

RRT is integral in the management of early and locally advanced lung cancer. In recent studies, researchers have indicated that cardiac events post-radiotherapy can decrease survival outcomes for patients. The aim of the current study was to determine risk factors that predispose patients to cardiac events post-radiotherapy.

Patients (n=600) at two UK healthcare institutions who were administered lung cancer RRT—stereotactic body radiotherapy, radical fractionated radiotherapy, and chemoradiotherapy—were included in the study. Those who had previously received multiple courses of radiotherapy to the chest were excluded. 

After a median follow-up of 31 months, 29% of patients exhibited pre-existing cardiac conditions, and 52 experienced cardiac events post-radiotherapy. Of these cardiac events, 37% were ischemic. Among patients who sustained ischemic events post-radiotherapy, 58% did not harbor a pre-existing cardiac condition.

Of note, 71% of cardiac events post-RRT happened in the first 2 years after radiotherapy. Subjects who received radical fractionated radiotherapy and concurrent radiotherapy were more likely to experience cardiac events.

Pre-existing cardiac conditions, Charlsons’ Comorbidity Index, and Qrisk3 scores were assessed. Of note, Qrisk3 scores indicated changes in population characteristics. The investigators identified post-radiotherapy cardiac events via electronic patient records.

In his interview with ecancer, Dr. Sun also stated that there exists no consensus as to the mechanism underlying cardiac events following RRT. He noted that it’s complicated to tease out a causative mechanism due to various confounding variables such as smoking. Moreover, it remains to be elucidated how low radiotherapy doses need to be before a protective effect on the heart is observed.

“A clinically significant proportion of patients developed cardiac toxicity following [RRT] for lung cancer,” concluded Dr. Sun et al. “Cardiac events occur much sooner after lung cancer radiotherapy than radiotherapy for breast cancer or lymphoma. Work is ongoing to identify greater number of patients and combine local data with data from national registry to aid analysis.”