Main Session
Sep 28
PQA 04 - Breast Cancer, Patient Reported Outcomes/QoL/Survivorship, Functional Radiation Medicine, Hematologic Malignancies, Palliative Care, and International/Global Oncology

2918 - Incidence and Dosimetric Correlates of Adverse Events in Stereotactic Arrhythmia Radioablation: A Prospective Registry Analysis

03:00pm - 04:00pm ET
Poster Hall - Exhibit Hall A
Screen: 11
POSTER

Presenter(s)

Raphael William, MD - University of Ottawa, Ottawa, ON

R. William1, C. J. Redpath2, C. Haberl2, A. M. Crean3, D. I. Paterson2, R. deKemp2, P. Nery2, M. Golian2, S. Hansom2, G. G. Cook1, and D. Tiberi1; 1Division of Radiation Oncology, The Ottawa Hospital, Ottawa, ON, Canada, 2Division of Cardiology, The University of Ottawa Heart Institute, Ottawa, ON, Canada, 3Centre for Cardiac Research Manchester, Manchester, Hong Kong

Purpose/Objective(s):

As Stereotactic Arrhythmia Radioablation (STAR) enters prospective trials, defining its specific toxicity profile is critical. We aimed to rigorously adjudicate adverse events (AEs) to distinguish true radiation-associated toxicity (RAE) from underlying disease progression and to identify dosimetric predictors of toxicity.

Materials/Methods:

We reviewed a cohort of 43 patients who underwent STAR for refractory VT. Suspected adverse events were documented and formally assessed utilizing the Common Terminology Criteria for Adverse Events (CTCAE) grading system. Total follow-up time was calculated from the date of radiotherapy delivery to the date of last follow-up or death. To evaluate dosimetric predictors, the cohort was stratified into quintiles of mean heart dose (across the entire contoured volume of the heart), which was then correlated to the presence of adverse events using Chi-square contingency analysis.

Results:

With a median follow-up of 1.39 years, the 43 patients yielded 75.1 patient-years of follow-up. A total of 4 clinically relevant adverse events (CTCAE > Grade 2/3) were documented (2 cases of pneumonitis, 2 cases of pericarditis), establishing a low complication rate of 0.053 events per patient-year. Onset time ranges varied considerably: pneumonitis events occurred at 1 and 5 months post-RT, while pericarditis emerged at 4 and 22 months post-RT. When evaluating factors contributing to adverse events (AE), PTV volume did not differ significantly between patients experiencing any AE vs. those who did not (mean 145.8 cc vs. 144.4 cc, p = 0.970). The stratification of PTV sizes by quintiles also showed no significant relationship with toxicity incidence (Chi-square p = 0.88).

For the pneumonitis cohort specifically, patients who developed pneumonitis exhibited slightly larger PTV volumes on average compared to those who did not (171.0 cc vs. 143.3 cc), but this was not statistically significant (p = 0.739). Evaluating lung-specific parameters for pneumonitis, the Mean Lung Dose was 2.68 Gy for pneumonitis patients compared to 2.64 Gy for unaffected patients (p = 0.936). Similarly, the irradiated lung volume (V7.4 Gy) averaged 312.1 cc for pneumonitis cases versus 301.1 cc for unaffected cases (p = 0.939). Stratifying mean lung dose into quintiles demonstrated no statistically significant clustering of pneumonitis events (Chi-square p = 0.414).

Conclusion:

In this small single center cohort with short term follow up , STAR appears well-tolerated with a low overall complication rate which resembles the well-established experience with lung stereotactic radiotherapy. Although delayed presentations mandate long-term monitoring, isolated toxicities did not significantly correlate with PTV volumes, or relevant Lung constraints. This implies that patient-specific factors, such as individual baseline lung disease or concurrent amiodarone use, might be primary drivers for these rare adverse events rather than strict dosimetric constraints.