Esophageal tolerance to high-dose stereotactic radiosurgery

PURPOSE: Esophageal tolerance is needed to guide the safe administration of stereotactic radiosurgery (SRS). We evaluated comprehensive dose-volume parameters of acute esophageal toxicity in patients with spinal metastasis treated with SRS. MATERIALS AND METHODS: From May 2008 to May 2011, 30 cases in 27 patients with spinal metastasis received single fraction SRS to targets neighboring esophagus. Endpoints evaluated include length (mm), volume (mL), maximal dose (Gy), and series of dose-volume thresholds from the dose-volume histogram (volume of the organ treated beyond a threshold dose). RESULTS: The median time from the start of irradiation to development of esophageal toxicity was 2 weeks (range, 1 to 12 weeks). Six events of grade 1 esophageal toxicity occurred. No grade 2 or higher events were observed. V(15) of external surface of esophagus was found to predict acute esophageal toxicity revealed by multivariate analysis (odds radio = 1.272, p = 0.047). CONCLUSION: In patients with spinal metastasis who received SRS for palliation of symptoms, the threshold dose-volume parameter associated with acute esophageal toxicity was found to be V(15) of external surface of esophagus. Restrict V(15) to external surface of esophagus as low as possible might be safe and feasible in radiosurgery.