3405 - Stereotactic Body Radiation Therapy for Ventricular Tachycardia is Safe and Effective: Results from a Large Retrospective Cohort

02:30pm - 03:45pm PT

Hall F

Screen: 21

POSTER

Presenter(s)

Keith Cengel, MD, PhD - University of Pennsylvania, Philadelphia, PA

J. Chojnowski¹, M. Chelius², M. Litt¹, T. Bhuiya¹, M. Raad¹, C. Jiang², S. Keane¹, J. Liang Tan¹, S. J. Feigenberg³, J. Arkles¹, C. Tschabrunn¹, S. Nazarian¹, D. Callans¹, D. S. Frankel¹, F. Marchlinski¹, M. M. Kim⁴, T. Markman¹, and K. A. Cengel³; ¹Hospital of the University of Pennsylvania, Philadelphia, PA, ²Department of Radiation Oncology, University of Pennsylvania, Philadelphia, PA, ³Department of Radiation Oncology, Perelman School of Medicine, University of Pennsylvania, Philadelphia, PA, ⁴Department of Radiation Oncology, Division of Medical Physics, Hospital of the University of Pennsylvania, Philadelphia, PA

Purpose/Objective(s):

Stereotactic body radiation therapy (SBRT) is a promising noninvasive treatment for refractory ventricular tachycardia (VT). Data are limited to small series with varying planning methodologies and limited toxicity follow-up. We report the largest single institution series.

Materials/Methods:

Patients with VT refractory to antiarrhythmic therapy who received cardiac SBRT from 2019-2024 were retrospectively analyzed. Under a single radiation oncologist, all patients underwent 4DCT simulation and treatment as an inpatient. Target volumes encompassed the arrhythmogenic scar delineated on the 4D scan integrating VT morphologies, imaging, and electroanatomic mapping data. Planning target volume (PTV) was a 3mm isotropic expansion from the internal target volume. Plans were LINAC-based VMAT, delivering 25Gy / 1fraction prescribed to the PTV. Toxicity was graded per CTCAEv5 where applicable, grouped as acute (</=90 days post-SBRT) and late (>90 days). Mitral regurgitation (MR) progression was defined as >2 point increase of MR International Database score.

Results:

45 patients underwent SBRT. Baseline characteristics included median age 69 years (IQR 63-77), male 84%, ECOG PS 0-1 43%, NYHA Class III-IV 43%, median left ventricular ejection fraction (LVEF) 30% (IQR 20-36.5). Patients had a median of 2 ICD shocks (IQR 0-3), 3 VT episodes (IQR 1-8) and 2 catheter ablations (IQR 2-3) 30 days prior to SBRT. Key dose metrics included: PTV D95% mean 23.6Gy (range 5.9-25.1), PTV volume mean 118cc (range 46-200), esophagus D0.03cc mean 7.7Gy (range 1.2-14.7), great vessel D0.03cc mean 11.8 (range 0.4-26.3), stomach D0.03cc mean 4.2Gy (range 0.2-12.4), heart-mean mean 8.4Gy (range 5.1-13.0).

Median follow-up was 8.3 months (IQR 2.2-22.0). Acute toxicity included nausea 11%, fatigue 9%, sternal pain 2% and malaise 4%, all low grade. Late toxicity included pneumonitis 11%, pleural effusion 4% and pericardial effusion 2%, all grade 1 (imaging finding, asymptomatic, not requiring intervention). LVEF was not impacted in the acute or late timeframe. Of patients with available imaging at 1 year follow up, 7/17 went on to develop worsening MR (2 required valve replacement, 1 improved with diuresis). At last follow-up, 62% of patients had died, none directly related to SBRT.

Compared to 30 days prior to SBRT, median change in average 30-day-rate of VT burden was -2 episodes from 1-3 months, -2 episodes from 3-6 months and -1.8 episodes from 6-12 months. At last follow up, median number of shocks post-SBRT was 0 (IQR 0-1).

Conclusion:

Cardiac SBRT is feasible among a range of performance statuses and target volumes; VT burden analysis is ongoing. Treatment appears safe with careful observance of constraints, incurring limited high grade toxicity. Further investigation regarding toxicity specific to cardiac substructures with dosimetric analysis is warranted and under current investigation at our center.