title: Dose escalation in the radiotherapy of non-small-cell lung cancer with aperture-based intensity modulation and photon beam energy optimization for non-preselected patients.
abstract: OBJECTIVE
  To verify the potential of aperture-based intensity-modulated radiotherapy (AB-IMRT) to realize dose escalation plans for non-preselected non-small-cell lung cancer (NSCLC) patients, using photon beam energy optimization.
  
  
  METHODS
  Seven cases of NSCLC were retrospectively studied. Clinical reference plans were made at 60 Gy by an experienced dosimetrist. Dose escalation was applied to PTV2, a subvolume within the main PTV1. Escalation plans were optimized by considering beam angles (table and gantry), energy (6 and 23 MV) and weights, for an increasing dose to the PTV2, starting from 66 Gy and keeping 30 fractions.
  
  
  RESULTS
  In five cases, doses over 78 Gy could be achieved before exceeding organs at risk (OARs) standard tolerance. Peripheral overdosages, as well as lung and spinal cord tolerance doses, limited escalation. Means+/-SD V(95%) parameters were (97.3+/-0.9)% for PTV1s and (96.7+/-2.2)% for PTV2s. Doses to OARs were also maintained at acceptable levels. Optimized plans made use of both low- and high-energy beams and had a similar number of monitor units compared to the 60 Gy clinical plans.
  
  
  CONCLUSIONS
  The AB-IMRT system can successfully realize dose escalation for a sizeable number of cases. Plans produced contained few large segments, and are applicable to a wide range of tumor volumes and locations.
authors.affiliation: Département de Physique, de Génie Physique et d'Optique, Université Laval, Québec, QC, Canada.
authors.forename: Jason
authors.initials: J
authors.lastname: St-Hilaire
authors.forename: Caroline
authors.initials: C
authors.lastname: Sévigny
authors.forename: Frédéric
authors.initials: F
authors.lastname: Beaulieu
authors.forename: François
authors.initials: F
authors.lastname: Germain
authors.forename: Caroline
authors.initials: C
authors.lastname: Lavoie
authors.forename: Anne
authors.initials: A
authors.lastname: Dagnault
authors.forename: Luc
authors.initials: L
authors.lastname: Gingras
authors.forename: Daniel
authors.initials: D
authors.lastname: Tremblay
authors.forename: Luc
authors.initials: L
authors.lastname: Beaulieu
mesh_terms: D002289:Carcinoma, Non-Small-Cell Lung / Q000473:pathology / Q000532:radiotherapy*; D019583:Dose Fractionation, Radiation; D004307:Dose-Response Relationship, Radiation; D006801:Humans; D021621:Imaging, Three-Dimensional; D008175:Lung Neoplasms / Q000473:pathology / Q000532:radiotherapy*; D017785:Photons / Q000627:therapeutic use; D011835:Radiation Protection; D011879:Radiotherapy Dosage; D011880:Radiotherapy Planning, Computer-Assisted / Q000379:methods*; D050397:Radiotherapy, Intensity-Modulated / Q000379:methods*; D012189:Retrospective Studies; D016896:Treatment Outcome