Room: Exhibit Hall | Forum 3
Purpose: Since cardiac substructures are not typically delineated or analyzed during radiation treatment planning, we evaluated the impact of incorporating cardiac substructure dose into toxicity modeling for radiation-induced pericardial effusion. We hypothesized that incorporating cardiac substructure dose would improve heart toxicity models.
Methods: One-hundred and forty-one stage III NSCLC patients, who received radiation therapy in a prospective clinical trial, were included in this analysis. The impact of DVH metrics (mean and max dose, V5â€“V70) for the total heart, left atrium, left ventricle, right atrium, and right ventricle on pericardial effusion toxicity (â‰¥grade 2, CTCAE v4.0 grading) were examined. Elastic net logistic regression, using repeated cross-validation (n=100 iterations, for avoiding observation selection bias), was conducted with cardiac-based DVH metrics as covariates. Models were trained with 75% of the data (training set), while the remaining 25% were reserved for testing model performance (test set). To assess the impact of cardiac substructure dose on toxicity modeling, we compared the following models: (a) standard model that included total heart DVH metrics-only; (b) models trained with both total heart and substructure DVH metrics; and (c) models using substructure DVH metrics-only. Model performance was assessed using AUC, calibration slope and intercept, and accuracy on the test set of each iteration.
Results: Grade 2 PCE incidence was 49.6% (n=70). The model using total heart+all substructure dose had the highest performance (AUC=0.819Â±0.063; calibration slope, intercept=1.824Â±1.197, -0.400Â±0.586; accuracy=0.731Â±0.070). Moreover, the standard model (total heart dose-only: AUC=0.799Â±0.063; calibration slope, intercept=4.445Â±5.432, -1.708Â±2.723; accuracy=0.696Â±0.085) was outperformed by many models that used various cardiac substructure DVH metrics only. Left atrium mean dose and right ventricle max dose were the most recurring predictors of toxicity.
Conclusion: Inclusion of cardiac substructure dose markedly improves toxicity modeling for radiation-induced pericardial effusion. Incorporation of cardiac substructures in treatment planning may better predict radiation-induced pericardial effusion.
Funding Support, Disclosures, and Conflict of Interest: This research was supported in part by The University of Texas MD Anderson Cancer Center Institutional Research Grant (IRG) Program.