Po-02-182 occurrence of pericardial and intra-pericardial space effusions with proton beam ablation

With large lesion formation, there is a possibility of perforation or other cardiac related tissue changes. These have not been well evaluated in a in situ model. The purpose of this study was to evaluate the pericardial effusion after pencil-beam scanned proton therapy on normal myocardium in swine in MRI. Therefore, 32 domestic swine underwent proton beam ablation to the left ventricle anterior wall, posterior wall, and apex. Each swine was subjected to monthly contrast-enhanced cardiac MRI to evaluate the post-irradiation effects. Importantly, the typical dose delivered after contouring, simulations, and treatment planning was between 30 and 40 Gy. With these deliveries, a pericardial effusion was seen in 18 swine. These were first seen 4 weeks after the radiation and showed resolution in 87% within 14 days. Actual pericarditis was seen in 2 pigs after the ablation. There was no evidence of dissection of myocardial tissue, nor steam pops or their equivalent with particle therapy. The animals appeared to show no distress or irritation. With the pathology at the time of study showed no presence of pericarditis and no other complications. Also, there was significant correlation between animals with mean dose to myocardium and the grade of PE. As such, pericardial effusions may occur in the setting of particle therapy. Of note, these are minor however and do not appear to be of clinical significance. Still, this suggests the need for careful monitoring of animals in the post-procedure setting.