Low rate of thoracic toxicity in palliative paraspinal single-fraction stereotactic body radiation therapy

Background: There has been an increase in the utilization of single-fraction stereotactic body radiation therapy (SBRT) to treat thoracic structures, but there have been few reports describing toxicity outcomes with this treatment. Methods: We evaluated 119 sites (114 patients) with no prior history of thoracic radiation were treated from 10/1/2003 to 10/27/2008 with single-fraction SBRT to thoracic structures. The median dose to the gross tumor volume was 2400 cGy (range 1800-2400 cGy), as was the median dose to the planning target volume (range 1600-2400 cGy). A detailed review of thoracic toxicities was performed to include pneumonitis or Grade 2 or higher esophageal and bronchial toxicity. In addition, we retrospectively contoured the esophagus and bronchus of 48 patients treated in 2004-2005, prior to the establishment of dose constraints to determine the range of doses that these structures received. Results: Of the contoured patients, the median dose to the hottest 1 cc (D1cc) of the esophagus was 1250 cGy (range 158-2572 cGy). The median bronchial D1cc was 1101 cGy (range 260-2211 cGy). At a median follow-up of 11.6 months, there were seven Grade 2 or higher esophageal toxicities, including one Grade 3 and one Grade 4 toxicities. There were two bronchial toxicities, one Grade 2 and one Grade 3. There were no cases of pneumonitis. Conclusions: High-dose single-fraction SBRT is well tolerated to the thoracic region, with most patients tolerating high doses to central structures without significant toxicity.