Inclusion of Incidental Radiation Dose to the Cardiac Atria and Ventricles Does Not Improve the Prediction of Radiation Pneumonitis in Advanced-Stage Non-Small Cell Lung Cancer Patients Treated With Intensity Modulated Radiation Therapy

Purpose: To evaluate if inclusion of incidental radiation dose to the cardiac atria and ventricles improves the prediction of Grade ≥3 radiation pneumonitis (RP) in advanced stage non-small cell lung cancer (AS-NSCLC) patients treated with intensity-modulated radiation therapy or volumetric-modulated arc therapy.
Material and methods: Using a bootstrap modelling approach, clinical parameters and dose-volume histogram (DVH) parameters of lungs and heart (assessing atria and ventricles separately and combined) were evaluated for RP prediction in 188 AS-NSCLC patients.
Results: After a median follow-up of 18.4 months, 26 patients (13.8%) developed RP. Only the median mean lung dose (MLD) differed between groups (15.3 Gy vs 13.7 Gy for the RP and non-RP group, respectively; p=0.004). The MLD showed the highest Spearman correlation coefficient (Rs) for RP (Rs=0.21; p<0.01). Most Rs of the lung DVH parameters exceeded those of the heart DVH parameters. After bootstrap modelling, the heart DVH parameters were seldom included in the model predicting Grade ≥3 RP. The optimal model for RP consisted of the parameters: MLD and cardiac comorbidity (area under the curve: 0.71).
Conclusion: Incidental dose to the cardiac atria and ventricles did not improve RP risk prediction in our cohort of AS-NSCLC patients.