title: Setup Error and Effectiveness of Weekly Image-Guided Radiation Therapy of TomoDirect for Early Breast Cancer.
abstract: OBJECTIVE
  This study investigated setup error and effectiveness of weekly image-guided radiotherapy (IGRT) of TomoDirect for early breast cancer.
  
  
  METHODS
  One hundred and fifty-one breasts of 147 consecutive patients who underwent breast conserving surgery followed by whole breast irradiation using TomoDirect in 2012 and 2013 were evaluated. All patients received weekly IGRT. The weekly setup errors from simulation to each treatment in reference to chest wall and surgical clips were measured. Random, systemic, and 3-dimensional setup errors were assessed. Extensive setup error was defined as 5 mm above the margin in any directions.
  
  
  RESULTS
  All mean errors were within 3 mm of all directions. The mean angle of gantry shifts was 0.6°. The mean value of absolute 3-dimensional setup error was 4.67 mm. In multivariate analysis, breast size (odds ratio, 2.82; 95% confidence interval, 1.00 to 7.90) was a significant factor for extensive error. The largest significant deviation of setup error was observed in the first week of radiotherapy (p < 0.001) and the deviations gradually decreased with time. The deviation of setup error was 5.68 mm in the first week and within 5 mm after the second week.
  
  
  CONCLUSIONS
  In this study, there was a significant association between breast size and significant setup error in breast cancer patients who received TomoDirect. The largest deviation occurred in the first week of treatment. Therefore, patients with large breasts should be closely observed on every fraction and fastidious attention is required in the first fraction of IGRT.
authors: Department of Radiation Oncology, St. Vincent's Hospital, College of Medicine, The Catholic University of Korea, Seoul, Korea.
authors: Mi Joo
authors: MJ
authors: Chung
authors: Department of Internal Medicine, Seoul, St. Mary's Hospital, College of Medicine, The Catholic University of Korea, Seoul, Korea.
authors: Guk Jin
authors: GJ
authors: Lee
authors: Department of Surgery, St. Vincent's Hospital, College of Medicine, The Catholic University of Korea, Seoul, Korea.
authors: Young Jin
authors: YJ
authors: Suh
authors: Department of Radiation Oncology, St. Vincent's Hospital, College of Medicine, The Catholic University of Korea, Seoul, Korea.
authors: Hyo Chun
authors: HC
authors: Lee
authors: Department of Radiation Oncology, St. Vincent's Hospital, College of Medicine, The Catholic University of Korea, Seoul, Korea.
authors: Sea-Won
authors: SW
authors: Lee
authors: Department of Radiation Oncology, St. Vincent's Hospital, College of Medicine, The Catholic University of Korea, Seoul, Korea.
authors: Songmi
authors: S
authors: Jeong
authors: Department of Radiation Oncology, Kyungpook National University, Daegu, Korea.
authors: Jeong Won
authors: JW
authors: Lee
authors: Department of Radiation Oncology, St. Vincent's Hospital, College of Medicine, The Catholic University of Korea, Seoul, Korea.
authors: Sung Hwan
authors: SH
authors: Kim
authors: Department of Radiation Oncology, St. Vincent's Hospital, College of Medicine, The Catholic University of Korea, Seoul, Korea.
authors: Dae Gyu
authors: DG
authors: Kang
authors: Department of Radiation Oncology, St. Vincent's Hospital, College of Medicine, The Catholic University of Korea, Seoul, Korea.
authors: Jong Hoon
authors: JH
authors: Lee
mesh_terms: D000328:Adult; D000368:Aged; D000369:Aged, 80 and over; D001943:Breast Neoplasms / Q000532:radiotherapy* / Q000601:surgery; D005260:Female; D006801:Humans; D007089:Image Enhancement / Q000379:methods; D008875:Middle Aged; D011829:Radiation Dosage; D011880:Radiotherapy Planning, Computer-Assisted / Q000379:methods; D061106:Radiotherapy Setup Errors; D061089:Radiotherapy, Image-Guided / Q000379:methods*; D050397:Radiotherapy, Intensity-Modulated / Q000379:methods; D015203:Reproducibility of Results
keywords: Breast neoplasms; Radiation; Radiotherapy setup error; TomoDirect