3007 - Observed Survival for Esophageal Cancer Patients Receiving High-Dose (>50Gy) vs. Low-Dose (=45.0 Gy) Radiation in Tri-Modality Therapy and Differences in Dose to Thoracic Organs at Risk (OAR)

C. N. Kersch, J. C. Burton, T. Sutton, M. Elsheikh, A. Yoo, N. Nabavizadeh, and S. Wood; Oregon Health and Science University, Portland, OR

Purpose/Objective(s): For operative candidates, tri-modal therapy with neoadjuvant chemoradiation (CRT) followed by esophagectomy is standard of care for locally advanced esophageal carcinoma. Radiation doses in North America are heterogeneous, ranging from 41.4 Gy to 50 Gy or more. As randomized data comparing radiation doses are lacking, we hypothesize that when comparing higher (=50 Gy) to lower (=45.0 Gy) neoadjuvant RT doses, oncologic outcomes are similar, but with an increased risk of adverse events. Our primary objective is to assess clinical outcomes in patients treated with neoadjuvant CRT to <45.0 Gy compared to higher-dose CRT at a single NCI-designated Comprehensive Cancer Center. Materials/

Methods: In this IRB-approved retrospective review, we collected patient demographics, tumor staging, tumor location within the esophagus, detailed radiation treatment records including dose volume histograms (DVH), and oncologic outcomes. Patients were over the age of 18, diagnosed with advanced (cT2–cT4 or node-positive) esophageal or gastroesophageal junction carcinoma, and underwent neoadjuvant CRT followed by esophagectomy between January 1, 2010 and December 31, 2019.
Results: This study included 287 treated with tri-modality therapy, of which 77 were treated to =45 Gy and 210 were treated with = 50.0Gy. Most patients were males (84%), with a diagnosis of adenocarcinoma (87.8%), and a median age of 65 years. The median follow-up from time of diagnosis was 69 months. The median OS was significantly worse in patients treated with =50.0 Gy as compared to =45 Gy (median 43.9 months versus median not reached, P=0.03). There were no significant differences in acute complications between the two groups. Detailed radiation records were available for 121 patients. There was significant variability in lung V20 (14.4%, IQR 9.5-18%), V5 (median 50.3%, IQR 39.5%-65.8%), VS5 (median 1750cc, IQR 1090-2480cc), and heart V45 (median 6.5%, IQR 4-11%), V30 (median 22.8%, IQR 15-35%), and V5 (median 99.5%, IQR 90-100%) within the evaluable cohort, with no correlation to total radiation dose or differences in OS.
Conclusion: For locally advanced esophageal carcinoma, neoadjuvant CRT to =45 Gy yields improved OS compared to higher pre-operative RT dosing, with similar peri-operative complication rates. Differences in standard OAR dose constraints do not explain this difference in OS. Further analysis is underway to assess potential mechanisms leading to this survival difference, including tumor location, RT dose to the left anterior descending artery, and RT delivery techniques.