Dose-volume parameters are needed to guide the safe administration of stereotactic ablative radiotherapy (SABR). We report on esophageal tolerance to high-dose hypofractionated radiation in patients treated with SABR. Thirty-one patients with spine or lung tumors received single- or multiple-fraction SABR to targets less than 1cm from the esophagus. End points evaluated include D5cc (minimum dose in Gy to 5cm3 of the esophagus receiving the highest dose), D2cc, D1cc, and Dmax (maximum dose to 0.01cm3). Multiple-fraction treatments were correlated using the linear quadratic and linear quadratic-linear/universal survival models. Three esophageal toxicity events occurred, including esophagitis (grade 2), tracheoesophageal fistula (grade 4-5), and esophageal perforation (grade 4-5). Chemotherapy was a cofactor in the high-grade events. The median time to development of esophageal toxicity was 4.1months (range 0.6-6.1months). Two of the three events occurred below a published D5cc threshold, all three were below a D2cc threshold, and one was below a Dmax threshold. We report a dosimetric analysis of incidental dose to the esophagus from SABR. High-dose hypofractionated radiotherapy led to a number of high-grade esophageal adverse events, suggesting that conservative parameters to protect the esophagus are necessary when SABR is used, especially in the setting of chemotherapy or prior radiotherapy.
- Stereotactic ablative radiotherapy
- Stereotactic body radiotherapy
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