A comparison of proton and photon radiotherapy in reducing cardiac exposure for patients receiving radiation therapy for distal and esophagogastric junction cancer.

167Background: Recent studies indicate that radiation exposure to heart may have a greater impact on perioperative cardiac morbidities than do other clinical factors. The purpose of this study is to investigate dose distributions of proton and photon treatment plans in patients (pts) with distal and esophagogastric junction (GEJ) carcinoma, focusing specifically on dose reduction to cardiac structures. Methods: Ten pts between 2010 and 2013 were included in this study. Three separate plans were generated for each patient: 3D proton plan, 3D photon plan, and Intensity modulated radiotherapy (IMRT) photon plan. The clinical target volume (CTV) consisted of the pre-operative extent of tumor plus a 10mm manual expansion in all directions. The planning target volume (PTV) was generated by a further expansion on the CTV ranging from 10-15mm. A dose of 50.4Gy given in 28 fractions was delivered to the PTV. All plans were optimized to allow 90% isodose coverage of at least 95% of the PTV. Dose-volume histograms were calculated and analyzed in order to compare plans between the three modalities. ANOVA and two-tailed paired t-tests were performed for all data parameters. Results: The 3D proton plans showed decreased dose to partial volumes of the entire heart, arteries, valves, atria, and ventricles in comparison to both the IMRT and 3D photon plans (see Table). The IMRT plans showed decreased dose delivered to the LAD artery, pericardium, and atria in comparison to the 3D photon plans (see Table). Conclusions: For pts receiving radiation therapy for distal esophageal and GEJ cancer, proton plans are technically feasible with adequate coverage while resulting in lower dose to cardiac structures. This may result in decreased cardiac toxicity and less complications in a multimodality setting. [Table: see text]