Single Institution Experience of Proton and Photon-based Postoperative Radiation Therapy for Non-small-cell Lung Cancer.

ABSTRACT Introduction Post-operative radiation therapy (PORT) for non-small cell lung cancer remains controversial with studies showing no overall survival benefit (OS) in the setting of excessive cardiopulmonary toxicity. Proton beam therapy (PBT) can potentially reduce toxicity with improved organ-at-risk sparing. We evaluated outcomes of PORT patients treated with PBT and Intensity modulated radiation therapy (IMRT). Methods Retrospective review of 136 PORT patients (61 PBT, 75 IMRT) treated from 2003-2016. A Kaplan-Meier analysis was performed to assess oncologic outcomes. A Cox regression was conducted to identify associated factors. Total toxicity burden (TTB) was defined as grade ≥ 2 pneumonitis, cardiac, or esophageal toxicity. Results Median OS was 76 and 46 months for PBT and IMRT with corresponding 1 and 5 year OS of 85.3%, 50.9% and 89.3%, 37.2% (p=0.38), respectively. V30Gy heart (OR 144.9, 95% CI; 2.91-7214, p=0.013) and V5Gy Lung (OR 15.8, 95% CI; 1.22-202.7, p=0.03) were predictive of OS. Organ-at-risk sparing was improved with PBT vs IMRT; mean heart 2.0Gy vs 7.4Gy (p Conclusions PBT improved cardiac and lung sparing and reduced toxicity compared to IMRT. Considering the impact of cardiopulmonary toxicity on PORT outcomes, PBT warrants prospective evaluation. MicroAbstract Post-operative radiation therapy (PORT) for NSCLC remains controversial and is associated with elevated cardiopulmonary toxicity. Recent advances in PORT techniques including proton beam therapy (PBT) may improve toxicity. We evaluated 136 patients treated with PORT at our institution. PBT resulted in improved heart and lung sparing with reduced toxicity rates. Proton based PORT should be evaluated prospectively.