Aug. 22, 2026
A first-in-human early feasibility study of using proton beam therapy for cardiac radioablation (CRA) found that the treatment reduced episodes of refractory ventricular tachycardia (VT). This novel therapeutic approach reduced episodes of the dangerous heart rhythm disorder by 79%. The study was published in Heart Rhythm.
The idea of applying proton beam therapy, used in cancer treatments, to treat patients with VT builds on Mayo Clinic's long-standing expertise in complex arrhythmia care and proton therapy for cancer. "Previous extensive preclinical Mayo Clinic work demonstrated that external beam radiation with protons can be accurately targeted to the heart to ablate abnormal tissue completely noninvasively, making this a potential treatment for VT. While photons, another radiotherapy modality, were already in use for therapy of VT, protons allow more-precise targeting with reduced radiation exposure of surrounding tissue," says Konstantinos Siontis, M.D., a cardiac electrophysiologist at Mayo Clinic in Rochester, Minnesota, and the lead investigator and first author of the study.
There was a vital need for this research because patients with refractory scar-mediated VT have limited options, despite medications and catheter ablation. "Developing less invasive, potentially safer and more effective treatment approaches for the most challenging VT cases is an unmet priority in electrophysiology," Dr. Siontis says. "This trial established basic feasibility, procedural safety and early efficacy before proton CRA could be considered a legitimate addition to the VT treatment armamentarium for patients who have run out of options."
Encouraging signals
The study shows that proton-based CRA can be integrated into a multidisciplinary workflow. The plan involves advanced imaging, electrophysiologic testing and motion-compensated radiotherapy preparation.
Study highlights:
- The researchers studied seven patients with left ventricular ejection fraction (LVEF) under 50% and refractory VT despite treatment with antiarrhythmic drugs and prior ablation.
- Proton therapy was delivered noninvasively as a single-fraction treatment of 30 Gy via two or three proton beams, without anesthesia.
- The mean age of patients was 68 years. Six patients were men.
- No acute or long-term probable or definite treatment-related serious adverse events occurred.
- Mean LVEF was 29% at baseline versus 25% at the end of follow-up. Valve function was preserved.
- VT burden declined by roughly 79% during follow-up up to two years, supporting both safety and efficacy.
"What stood out was how well the procedure was tolerated in a cohort with advanced cardiomyopathy, low LVEF and multiple failed prior ablations. We didn't see any clear valvular, pericardial or coronary toxicity signals that are a theoretical concern with cardiac radiation. The VT reduction across most of the seven patients was encouraging given how refractory their arrhythmias were," Dr. Siontis says.
Next steps
Larger multicenter cohorts, longer follow-up and better understanding of long-term safety and durability of VT suppression are still needed.
"Further research and development are important to refine target delineation and delivery of proton beam to the heart, such as synchronizing the beam delivery to each heartbeat. These improved techniques are expected to further improve the targeting accuracy and reduce toxicities of the treatment," Dr. Siontis says.
Broader access to proton beam therapy depends on the availability of proton facilities, which are more limited than those for photon radiotherapy.
The study shows a pattern distinctive to Mayo Clinic: translating a technology mature in one specialty into a different discipline to address a clinical problem. "It took electrophysiology, radiation oncology and physics collaborating over years of preclinical work before treating the first patient," Dr. Siontis says. "This translation of preclinical knowledge to first-in-human clinical innovation demonstrates Mayo's leadership and commitment in bringing innovative therapies to patients."
For more information
Figure 1F from: Siontis KC, et al. Early feasibility study of catheter-free cardiac radioablation with proton beams for refractory ventricular tachycardia. Heart Rhythm. In press.
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