3448 - Dosimetric Comparison of Carbon Ion Beam Therapy and SBRT for Ventricular Arrhythmia

02:30pm - 03:45pm PT

Hall F

Screen: 21

POSTER

Presenter(s)

Mayumi Ichikawa, MD, PhD - Yamagata University School of Medicine, Yamagata, Yamagata

M. Ichikawa¹, Y. Miyasaka², N. Hashimoto³, M. Komatsu¹, K. Uematsu¹, N. Yano¹, T. Kaneko¹, T. Ono¹, H. Akamatsu¹, Y. Hagiwara¹, H. Sato¹, H. Souda², T. Iwai², T. Arimoto³, M. Watanabe³, and M. Koto¹; ¹Department of Radiation Oncology, Yamagata University Faculty of Medicine, Yamagata, Japan, ²Department of Heavy Particle Medical science, Yamagata University Graduate School of Medical Science, Yamagata, Japan, ³Department of Cardiology, Pulmonology, and Nephrology, Yamagata University School of Medicine, Yamagata, Japan

Purpose/Objective(s): Stereotactic body radiation therapy (SBRT) has demonstrated promising anti-arrhythmic effects for ventricular tachycardia (VT) refractory to catheter ablation. However, the use of SBRT requires irradiation from multiple angles, leading to increased exposure of low- and medium-dose regions, which has been associated with adverse events such as pericarditis, pneumonitis, and pericardial effusion. In contrast, carbon ion beam therapy offers superior dose conformity and linear energy transfer (LET) characteristics, potentially reducing radiation exposure to surrounding normal tissues while maintaining effective target coverage. This study compares the dosimetric advantages of volumetric modulated arc therapy (VMAT) and carbon ion beam therapy (CIRT) for VT.

Materials/Methods: Eight patients with VT previously treated with catheter ablation at our institution were included in this study. Target volumes were delineated based on cardiac CT imaging and electroanatomic mapping, with a 5 mm PTV margin applied. Treatment plans were generated for both VMAT and scanning carbon ion beam therapy. Dose constraints for organs at risk (OARs) were set arbitrarily, and treatment was prescribed at 25 Gy in a single fraction to the PTV, targeting a D95 within the 75–85% isodose level (IDL). Dose constraints were prioritized as OAR > PTV coverage. VMAT plans were generated using four arcs (approximately 180°rotation per arc, two full passes), while CIRT plans utilized two fields. Dose distributions to the PTV, target, and surrounding normal tissues were analyzed and compared.

Results: The D95 of PTV is superior in CIRT plans (CIRT vs. VMAT: 16.5 ± 4.0 Gy vs. 14.4 ± 3.5 Gy, p= 0.017), with a significantly improved the V95% of Target (CIRT vs. VMAT: 95.2 ± 5.4% vs. 84.9 ± 10.9%, p = 0.012). The dose of OARs was lower in the CIRT plans than in the VMAT plans. CIRT plans also resulted in significantly lower lung V7Gy (CIRT vs. VMAT: 55.9 ± 34.3 cc vs. 102.6 ± 61.7 cc, p = 0.028), indicating reduced lung dose exposure. There was no statistically significant (p = 0.324) in V16Gy of heart, but CIRT plans were 10 cc smaller than VMAT plans.

Conclusion: CIRT achieved a higher dose coverage for the PTV and target while reducing radiation exposure to the surrounding normal tissues compared to VMAT. Moving forward, we plan to implement carbon-ion radiotherapy for cardiac radiation treatment.