title: Monte Carlo calculations support organ sparing in Deep-Inspiration Breath-Hold intensity-modulated radiotherapy for locally advanced lung cancer.
abstract: OBJECTIVE
  Studies indicate that Deep-Inspiration Breath-Hold (DIBH) is advantageous over Free-Breathing (FB) for locally advanced lung cancer radiotherapy. However, these studies were based on simplified dose calculation algorithms, potentially critical due to the heterogeneous nature of the lung region. Using detailed Monte-Carlo (MC) calculations, a comparative study of DIBH vs. FB was therefore designed.
  
  
  METHODS
  Eighteen locally advanced lung cancer patients underwent FB and DIBH CT imaging and treatment planning with the Anisotropic-Analytical-Algorithm (AAA) for intensity-modulated-radiotherapy or volumetric-modulated-arc-therapy using 66Gy in 33 fractions. All plans were re-calculated with MC.
  
  
  RESULTS
  Relative to FB, the total lung volume increased 86.8% in DIBH, while the gross tumor volume decreased 14.8%. MC revealed equally under- and over-dosage of the target for FB and DIBH, compared to AAA. For the Organs-At-Risk (OARs), DIBH reduced the mean heart dose by 25.5% (AAA) vs. 12.6% (MC), the total lung V5Gy/V20Gy by 9.0/20.0% (AAA) vs. 11.6/19.9% (MC).
  
  
  CONCLUSIONS
  MC calculations revealed (i) that DIBH compared with FB can significantly reduce the dose to the OARs even if the treatment planning is carried out with AAA, and (ii) inferior target dose coverage compared to AAA, irrespectively of FB and DIBH. The dose deviations were similar for FB and DIBH. The observed inferior target dose coverage relates therefore to the treatment planning algorithm rather than breathing technique.
authors.affiliation: Center for Nuclear Technologies, Technical University of Denmark, DTU Risø Campus, Roskilde, Denmark; Department of Oncology, Radiotherapy Research Unit, Herlev Hospital, University of Copenhagen, Denmark. Electronic address: wivott01@heh.regionh.dk.
authors.forename: Wiviann
authors.initials: W
authors.lastname: Ottosson
authors.affiliation: Center for Nuclear Technologies, Technical University of Denmark, DTU Risø Campus, Roskilde, Denmark; Department of Oncology, Radiotherapy Research Unit, Herlev Hospital, University of Copenhagen, Denmark.
authors.forename: Patrik
authors.initials: P
authors.lastname: Sibolt
authors.affiliation: Department of Oncology, Radiotherapy Research Unit, Herlev Hospital, University of Copenhagen, Denmark.
authors.forename: Christina
authors.initials: C
authors.lastname: Larsen
authors.affiliation: Department of Oncology, Herlev Hospital, University of Copenhagen, Denmark.
authors.forename: Jon A
authors.initials: JA
authors.lastname: Lykkegaard Andersen
authors.affiliation: Department of Oncology, Herlev Hospital, University of Copenhagen, Denmark.
authors.forename: Svetlana
authors.initials: S
authors.lastname: Borissova
authors.affiliation: Department of Oncology, Herlev Hospital, University of Copenhagen, Denmark.
authors.forename: Anders
authors.initials: A
authors.lastname: Mellemgaard
authors.affiliation: Department of Oncology, Radiotherapy Research Unit, Herlev Hospital, University of Copenhagen, Denmark.
authors.forename: Claus F
authors.initials: CF
authors.lastname: Behrens
mesh_terms: D000368:Aged; D000465:Algorithms; D062485:Breath Holding; D005260:Female; D006321:Heart / Q000033:anatomy & histology / Q000528:radiation effects; D006801:Humans; D008175:Lung Neoplasms / Q000532:radiotherapy*; D008297:Male; D008875:Middle Aged; D009010:Monte Carlo Method; D059351:Organ Sparing Treatments / Q000379:methods*; D011880:Radiotherapy Planning, Computer-Assisted / Q000379:methods*; D050397:Radiotherapy, Intensity-Modulated / Q000379:methods
keywords: DIBH; IMRT; Lung cancer; Monte Carlo; Treatment planning; VMAT