Esophageal tolerance to high-dose stereotactic ablative radiotherapy

Abstract

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 1 cm from the esophagus. End points evaluated include D(5cc) (minimum dose in Gy to 5 cm(3) of the esophagus receiving the highest dose), D(2cc) , D(1cc) , and D(max) (maximum dose to 0.01 cm(3) ). 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 4.1 months (range 0.6-6.1 months). Two of the three events occurred below a published D(5cc) threshold, all three were below a D(2cc) threshold, and one was below a D(max) 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.

Dosimetric predictors of esophageal toxicity after stereotactic body radiotherapy for central lung tumors

“…[23] This was a smaller series and included patients receiving SBRT as a boost to conventionally fractionated therapy, and the authors only analyzed a limited number of predetermined D v endpoints. Another series of central lung SBRT included a subset of 15 patients with tumors near the esophagus treated with 6 fractions of 8Gy and observed an overall 11% rate of acute Grade 1–2 esophagitis.…”

Dose-Volume Predictors of Esophagitis After Thoracic Stereotactic Body Radiation Therapy

“…4,6,7 Stephans et al 5 demonstrated a late gradeZ3 incidence of 3.8%; however, both events were tracheoesophageal fistulas in patients given adjuvant VEGF-modulating agents. Abelson et al 16 reported a gradeZ4 toxicity rate of 6.4%. In our analysis, we demonstrated gradeZ2 and gradeZ3 esophagitis rates of 5.7% and 0.6%, respectively-in light of the few gradeZ3 events, it is therefore important to note that our dosimetric parameters are most predictive of the less severe grade 2 toxicities.…”

“…In an analysis of 182 patients treated with single-fraction SRS, Cox et al 7 revealed that D2.5 mL was the best predictor of esophagitis (P < 0.0006). In a cohort of 31 patients (treated with a wide variety of SBRT fractionation schemes), Abelson et al 16 studied the equivalent single-fraction BED3 to 1.0, 2.0, 5.0 mL, and maximal point and determined that severe toxicities occurred near previously published thresholds. Other studies have recommended the use of V15 in single-fraction SRS to prevent esophagitis.…”

Submillimeter alignment of more than three contiguous vertebrae in spinal SRS/SBRT with 6‐degree couch

“…Comparing to spinal cord, the dose constraints to the esophagus in spinal SRS/SBRT are less understood. Even though the dose constraint standard has yet been established for esophagus, partial volume constraints, such as dose to a small volume of 1 to 5 cc (D1 cc to D5 cc), and Dmax have been suggested in previous reports and used in clinical trials 18, 19, 20. Unlike a point dose, such as Dmax to the cord, which is unlikely to be effected by the extra vertebrae, a partial volume parameter, like D1 cc, generally increases with move critical structure volume receiving dose.…”