In this phase I/II prospective trial, Dr. Robinson and Dr. Cuculich treated 19 patients who had life-threatening cardiac arrhythmia with a single fraction (25 Gy) of SBRT. They previously reported that ENCORE led to a 94% reduction in VT episodes in the first six months. Longer-term follow up data now show that the effect persisted in 78% of patients for more than two years after the radiation treatment.

Overall survival was 74% after the first year and 52% after the second year. Nine patients died – six from cardiac deaths (heart failure and VT recurrence) and three from non-cardiac deaths (accident, amiodarone toxicity, pancreatic cancer). Late serious adverse events included two cases of pericardial effusion, or irritation of the lining of the heart, and one fistula between the stomach and the heart that required surgical repair; all three events occurred more than two years after treatment.


Dr. Robinson said that these adverse events were not surprising given the condition of the patients they were treating. He also noted that the team is learning how to address these issues in the future. “Patients come to us as a last line of defense,” he said. “They have few or no other options. Often, the primary reason we are treating them is because they were too sick to have more catheter ablation. It’s very similar when you compare surgery to SBRT for patients with lung cancer. A patient who is sick to begin with and who has heart failure will continue to have heart failure admissions to the hospital. The subsequent failures don't seem to be clearly related to the radiation, but ample other research has shown that radiation exposure can result in long-term cardiac injury. Given the relative novelty of this treatment approach, we are following our patients closely, conducting trials to gather more data and being careful not to make assumptions at this point.”

An additional benefit to treatment, said Dr. Robinson, was a reduction in the medications patients were taking, which resulted in fewer medication-related side effects and a higher quality of life. “These patients were on heavy doses of medications, with side effects such as liver damage, lung damage, nausea and thyroid problems. After they were treated, we could dramatically reduce their medications. We saw reduced VT, reduced medication and improved quality of life, at least in the intermediate term.”

Dr. Robinson said ENCORE is currently best used for people who have cardiac injury, develop an arrhythmia and have already tried catheter ablation with no success. In the future, ENCORE could potentially benefit thousands to tens of thousands of patients, he said. Though hundreds of thousands of people who die of cardiovascular disease experience arrhythmia before they die, many have sudden death and there is no opportunity to treat them.

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