title: Spine radiosurgery: a dosimetric analysis in 124 patients who received 18 Gy.
abstract: OBJECTIVE
  To define the safely tolerated doses to organs at risk (OARs) adjacent to the target volume (TV) of spine radiosurgery (SRS) with 18-Gy in a single fraction.
  
  
  METHODS
  A total of 124 patient cases with 165 spine metastases were reviewed. An 18-Gy single-fraction regimen was prescribed to the 90% isodose line encompassing the TV. A constraint of 10 Gy to 10% of the spinal cord outlined 6 mm above and below the TV was used. Dosimetric data to OARs were analyzed.
  
  
  RESULTS
  A total of 124 patients (100%) were followed-up, and median follow-up time was 7 months (1-50 months). Symptoms and local control were achieved in 114 patients (92%). Acute Radiation Therapy Oncology Group (RTOG) grade 1 oral mucositis occurred in 11 of 11 (100%) patients at risk for oropharyngeal toxicity after cervical spine treatment. There were no RTOG grade 2-4 acute or late complications. Median TV was 43.2 cc (5.3-175.4 cc) and 90% of the TV received median dose of 19 Gy (17-19.8 Gy). Median (range) of spinal cord maximum dose (Dmax), dose to spinal cord 0.35 cc (Dsc0.35), and cord volume receiving 10 Gy (Vsc10) were 13.8 Gy (5.4-21 Gy), 8.9 Gy (2.6-11.4 Gy) and 0.33 cc (0-1.6 cc), respectively. Other OARs were evaluated when in proximity to the TV. Esophagus (n=58), trachea (n=28), oropharynx (n=11), and kidneys (n=34) received median (range) V10 and V15 of 3.1 cc (0-5.8 cc) and 1.2 cc (0-2.9 cc), 2.8 cc (0-4.9 cc), and 0.8 cc (0-2.1 cc), 3.4 cc (0-6.2 cc) and 1.6 cc (0-3.2 cc), 0.3 cc (0-0.8 cc) and 0.08 cc (0-0.1 cc), respectively.
  
  
  CONCLUSIONS
  Cord Dmax of 14 Gy and D0.35 of 10 Gy are safe dose constraints for 18-Gy single-fraction SRS. Esophagus V10 of 3 cc and V15 of 1 cc, trachea V10 of 3 cc, and V15 of 1 cc, oropharynx V10 of 3.5 cc and V15 of 1.5 cc, kidney V10 of 0.3 cc, and V15 of 0.1 cc are planning guidelines when these OARs are in proximity to the TV.
authors.affiliation: Institute of Cancer Sciences, University of Glasgow, Glasgow, United Kingdom.
authors.forename: Stefano
authors.initials: S
authors.lastname: Schipani
authors.forename: Winston
authors.initials: W
authors.lastname: Wen
authors.forename: Jain-Yue
authors.initials: JY
authors.lastname: Jin
authors.forename: Jin Koo
authors.initials: JK
authors.lastname: Kim
authors.forename: Samuel
authors.initials: S
authors.lastname: Ryu
mesh_terms: D000328:Adult; D000368:Aged; D000369:Aged, 80 and over; D002574:Cervical Vertebrae; D004947:Esophagus / Q000528:radiation effects; D005260:Female; D006801:Humans; D007668:Kidney / Q000528:radiation effects; D008159:Lumbar Vertebrae; D008297:Male; D020714:Maximum Tolerated Dose; D008875:Middle Aged; D058958:Organs at Risk / Q000528:radiation effects*; D009960:Oropharynx / Q000528:radiation effects; D016634:Radiosurgery; D011879:Radiotherapy Dosage; D012189:Retrospective Studies; D013116:Spinal Cord / Q000528:radiation effects; D013125:Spinal Neoplasms / Q000556:secondary* / Q000601:surgery*; D013280:Stomatitis / Q000209:etiology; D013904:Thoracic Vertebrae; D014132:Trachea / Q000528:radiation effects