Comparison of proton and photon therapy in stereotactic arrhythmia radioablation for ventricular tachycardia

Background and Purpose

Ventricular tachycardia (VT) is a life-threatening arrhythmia commonly treated with catheter ablation; however, some cases remain refractory. Stereotactic arrhythmia radioablation (STAR) offers a non-invasive alternative. While photon-based STAR is effective, proton therapy may improve dose conformity and spare critical organs at risk (OARs), including the heart itself. The aim of this study was to compare the dose-volume metrics between proton and photon therapy for VT.

Materials and Methods

We retrospectively analyzed 34 VT patients who received photon STAR. Proton STAR plans were generated using robust optimization in a commercial treatment planning system to deliver the same prescription dose of 25 Gy in a single fraction. Dose-volume metrics, including D₉₉, D₉₅, D_mean, and $D_{{0.03cm}^3}$, were extracted for critical OARs (heart, lungs, cardiac-chambers) and target. Shapiro-Wilk tests were used to assess normality, with paired t-tests or Wilcoxon signed-rank tests for statistical comparisons between modalities, with Bonferroni correction applied for multiple comparisons.

Results

Proton and photon plans achieved comparable target coverage, with CTV D₉₅ of 25.8 [21.6–28.7] Gy(RBE) vs. 27.2 [21.6–29.3] Gy (p < 0.001). Proton therapy significantly reduced OAR doses, including heart D_mean (3.6 ± 1.5 Gy(RBE) vs. 5.5 ± 2.0 Gy, p < 0.001) and lungs D_mean (0.6 [0.0–1.9] Gy(RBE) vs. 1.2 [0.2–2.6] Gy, p < 0.001), while maintaining optimal target coverage.

Conclusion

Proton therapy for STAR demonstrated significant potential for OARs sparing compared to photon therapy for VT, while maintaining equivalent target coverage. These findings highlight the potential of proton therapy to improve outcomes for VT patients.