Low Incidence of esophageal toxicity following Lung SBRT: Are current esophageal dose constraints too conservative?

Publication date: Available online 2 March 2018
Source:International Journal of Radiation Oncology*Biology*Physics
Author(s): Vivian Yau, Patricia Lindsay, Lisa Le, Anthea Lau, Olive Wong, Daniel Glick, Andrea Bezjak, B.C.John Cho, Andrew Hope, Alex Sun, Meredith Giuliani
IntroductionTumours in close proximity to the esophagus present a challenge for lung SBRT, as potential esophageal toxicity must be balanced with the goal of tumour control. The purpose of this study was to explore and quantify the relationship between esophageal dose and toxicity.MethodsWe conducted this analysis based on a prospective study of patients treated with SBRT at our institution from October 2004 to December 2015. Most patients were treated with 54Gy/3, 48Gy/4 alternate days, or 60Gy/8 daily. Toxicity was prospectively graded using CTCAE v3.0. Logistic regression was used to estimate the risk of esophageal toxicity as a function of radiotherapy dose, in 2-Gy-equivalent dose (EQD2), using an alpha-beta ratio of 3 Gy in the linear-quadratic model.Results632 patients were analyzed. The median follow up was 20.8 months. Median overall survival was 35.3 months. The rate of late or acute, grade 1 or greater esophageal toxicity, including dysphagia, odynophagia, and esophagitis, was 3.3% (n=21). The median (range) esophageal doses were 11.8Gy (0.2-48.2Gy), 10.34Gy (0.17- 44.5Gy), and 9.63Gy (0.08- 43Gy) for Dmax, D1cc and D2cc, respectively. A 15% risk of esophageal toxicity was associated with EQD2 of Dmax 141.6Gy, D1cc 123.61, and D2cc 117.6Gy. Of the 21 patients who experienced esophageal toxicity, only 1 patient had grade 3 toxicity and the remainder had grade 2 or lower toxicity.Discussion: The observed rate of toxicity was low, despite some patients receiving relatively high doses to the esophagus. A prospective study in a targeted population, for example patients with ultracentral tumours, may provide more accurate dose-toxicity parameters.



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