Low Incidence of Esophageal Toxicity After Lung Stereotactic Body Radiation Therapy: Are Current Esophageal Dose Constraints Too Conservative?

PURPOSE

To explore and quantify the relationship between esophageal dose and toxicity in the setting of lung stereotactic body radiation therapy (SBRT).

METHODS AND MATERIALS

This analysis was conducted on the basis of a prospective study of patients treated with SBRT at our institution from October 2004 to December 2015. Most patients were treated with 54 Gy/3 fractions, 48 Gy/4 fractions alternate days, or 60 Gy/8 fractions daily. Toxicity was prospectively graded using Common Terminology Criteria for Adverse Events version 3.0. Logistic regression was used to estimate the risk of esophageal toxicity as a function of radiation therapy dose, in 2-Gy-equivalent dose, using an α/β ratio of 3 Gy in the linear-quadratic model.

RESULTS

A total of 632 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 esophageal toxicity, including dysphagia, odynophagia, and esophagitis, was 3.3% (n = 21). The median (range) esophageal doses were 11.8 Gy (0.2-48.2 Gy), 10.34 Gy (0.17-44.5 Gy), and 9.63 Gy (0.08-43 Gy) for Dmax, D1cc, and D2cc, respectively. A 15% risk of esophageal toxicity was associated with a 2-Gy-equivalent dose of Dmax 141.6 Gy, D1cc 123.61 Gy, and D2cc 117.6 Gy. Of the 21 patients who experienced esophageal toxicity, only 1 patient had grade 3 toxicity, and the remainder had grade 2 or lower toxicity.

CONCLUSIONS

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 tumors, may provide more accurate dose-toxicity parameters.