title: Validating the RTOG-endorsed brachial plexus contouring atlas: an evaluation of reproducibility among patients treated by intensity-modulated radiotherapy for head-and-neck cancer.
abstract: OBJECTIVE
  To evaluate interobserver variability for contouring the brachial plexus as an organ-at-risk (OAR) and to analyze its potential dosimetric consequences in patients treated with intensity-modulated radiotherapy (IMRT) for head-and-neck cancer.
  
  
  METHODS
  Using the Radiation Therapy Oncology Group (RTOG)-endorsed brachial plexus contouring atlas, three radiation oncologists independently delineated the OAR on treatment planning computed-tomography (CT) axial scans from 5 representative patients undergoing IMRT to a prescribed dose of 70 Gy for head-and-neck cancer. Dose-volume histograms for the brachial plexus were calculated, and interobserver differences were quantified by comparing various dosimetric statistics. Qualitative analysis was performed by visually assessing the overlapping contours on a single beam's eye view.
  
  
  RESULTS
  Brachial plexus volumes for the 5 patients across observers were 26 cc (18-35 cc), 25 cc (21-30 cc), 29 cc (28-32 cc), 29 cc (23-38 cc), and 29 cc (23-34 cc). On qualitative analysis, minimal variability existed except at the inferolateral portion of the OAR, where slight discrepancies were noted among the physicians. Maximum doses to the brachial plexus ranged from 71.6 to 72.6 Gy, 75.2 to 75.8 Gy, 69.1 to 71.0 Gy, 76.4 to 76.9 Gy, and 70.6 to 71.4 Gy. Respective volumes receiving doses greater than 60 Gy (V60) were 8.6 to 10.9 cc, 6.2 to 8.1 cc, 8.2 to 11.6 cc, 8.3 to 10.5 cc, and 5.6 to 9.8 cc.
  
  
  CONCLUSIONS
  The RTOG-endorsed brachial plexus atlas provides a consistent set of guidelines for contouring this OAR with essentially no learning curve. Adoption of these contouring guidelines in the clinical setting is encouraged.
authors.affiliation: Department of Radiation Oncology, University of California Davis School of Medicine, Sacramento, California, USA.
authors.forename: Sun K
authors.initials: SK
authors.lastname: Yi
authors.forename: William H
authors.initials: WH
authors.lastname: Hall
authors.forename: Mathew
authors.initials: M
authors.lastname: Mathai
authors.forename: Arthur B
authors.initials: AB
authors.lastname: Dublin
authors.forename: Vishal
authors.initials: V
authors.lastname: Gupta
authors.forename: James A
authors.initials: JA
authors.lastname: Purdy
authors.forename: Allen M
authors.initials: AM
authors.lastname: Chen
mesh_terms: D001917:Brachial Plexus / Q000000981:diagnostic imaging* / Q000528:radiation effects; D020516:Brachial Plexus Neuropathies / Q000517:prevention & control; D006258:Head and Neck Neoplasms / Q000532:radiotherapy*; D006801:Humans; D008488:Medical Illustration; D015588:Observer Variation; D058958:Organs at Risk / Q000000981:diagnostic imaging* / Q000528:radiation effects; D011859:Radiography; D011879:Radiotherapy Dosage; D011880:Radiotherapy Planning, Computer-Assisted / Q000379:methods*; D050397:Radiotherapy, Intensity-Modulated / Q000379:methods*; D015203:Reproducibility of Results