The following is a summary of “Cardiopulmonary Toxicity Following Intensity-Modulated Proton Therapy (IMPT) Versus Intensity-Modulated Radiation Therapy (IMRT) for Stage III Non-Small Cell Lung Cancer” published in the December 2022 issue of Clinical Lung Cancer by Yu et al.

Compared to intensity-modulated radiation therapy (IMRT), intensity-modulated proton therapy (IMPT) has the potential to lower the radiation exposure to healthy tissues and organs. Researchers postulated that patients with Stage III NSCLC would experience less cardiovascular toxicities with IMPT than they would with IMRT. In this study, they compared the outcomes of IMPT (n=35, 21%) with IMRT (n=128, 79%) in 163 consecutively treated patients with biopsy-proven, stage III NSCLC. Variables such as patient, tumor, and therapy background were examined. The Kaplan-Meier estimate was used to determine overall survival (OS), freedom from distant metastasis (FFDM), freedom from locoregional relapse (FFLR), and cardiopulmonary toxicities (CTCAE v5.0). The final model was based on univariate Cox regressions.

Patients who were able to be followed for an extended period of time were followed for a median of 25.5 months (range, 4.6-58.1 months). The median radiation therapy dosage was 60 (range, 45-72) Gy [RBE]. There were no modality-dependent differences in OS, FFDM, or FFLR. When compared to IMRT, IMPT resulted in much higher pulmonary and cardiac dosimetric sparing. Pneumonitis of grade 3 or higher and cardiac events of grade 3 or higher were both shown to be less common among patients who underwent IMPT (HR 0.25, P=.04 and HR 0.33, P=.08, respectively). There was an elevated risk of pneumonitis grade 3 or above in patients with pretreatment estimated diffusing capacity for carbon monoxide of 57% (HR 2.8, P=.04) and/or forced expiratory volume in the first second less than equal to 61% (HR 3.1, P=.03).

Without sacrificing tumor control, IMPT is associated with a lower incidence of clinically severe pneumonitis and cardiac events compared to IMRT in stage III NSCLC. For high-risk individuals with low pulmonary function before treatment, IMPT may be a safer option.