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Analysis of Normal Tissue Response in the Esophagus Between IMRT and Proton Therapy Using Imaging Biomarkers

L Court

L Court1*, J Niedzielski1,2, U Titt1 , J Yang1 , R Mohan1 , D Mirkovic1 , F Stingo3 , D Gomez1 , Z Liao1 , M Martel1 , T Briere1 , L Court1 , (1) The University of Texas MD Anderson Cancer Center, Houston, TX, (2) University of Colorado, Aurora, CO, (3) University of Florence, Florence, Italy


SU-F-FS1-2 (Sunday, July 30, 2017) 2:05 PM - 3:00 PM Room: Four Seasons 1

Purpose: To determine if there exists any significant difference in normal tissue toxicity of the esophagus between IMRT or proton therapy for the treatment of non-small-cell lung cancer, with toxicity quantified using a novel CT imaging biomarker.

Methods: A total of 134 study patients, (n=49 treated with proton therapy, n=85 with IMRT) treated in a randomized trial, had the previously validated esophageal toxicity CT imaging biomarker, esophageal expansion, quantified weekly during radiation therapy. Esophagitis grade (CTCAE v3.0) was also quantified on a weekly basis during treatment. Differences in the incidence of esophagitis grade and imaging biomarker metric value were compared between the two modalities with the chi-squared test and the Kruskal-Wallis ANOVA, respectively. The imaging biomarker dose-response was also compared between modalities using esophagus equivalent uniform dose, as well as delivered dose to an isotropic esophageal subvolume.

Results: No statistically significant difference in incidence of esophagitis grade (p=0.42) or the esophageal expansion imaging biomarker between cohorts (p>0.05, for all metrics) was found. The distribution of imaging biomarker metric values had similar distributions between treatment arms, despite a slightly higher dose-volume in the proton arm (p>0.05). Imaging biomarker dose-response was similar between modalities for dose quantified as esophagus equivalent uniform dose and delivered esophageal subvolume dose. Regardless of treatment modality, there was high variability in imaging biomarker response, as well as esophagitis grade, for similar esophageal doses between patients.

Conclusion: There was no significant difference in esophageal toxicity from either proton or photon-based radiation therapy as quantified by esophagitis grade, or the esophageal expansion radiation-response imaging biomarker. Severity of esophageal toxicity is no greater with proton therapy than IMRT.

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