title: Adaptive radiotherapy for locally advanced non-small cell lung cancer, can we predict when and for whom?
abstract: BACKGROUND
  Adaptive radiotherapy (ART) could be a tool to reduce toxicity and to facilitate dose escalation in stage III NSCLC. Our aim was to identify the most appropriate time and potential benefit of ART.
  
  
  METHODS
  We analyzed volume reduction and dosimetric consequences of 41 patients who were treated with concurrent (cCRT) (n = 21) or sequential (sCRT) chemoradiotherapy to a median dose of 70 Gy, 2 Gy/F. At every treatment fraction a cone-beam CT (CBCT) was performed. The gross tumor volume (GTV-T) was adapted (exclusion of lymph nodes) to create the GTV-T-F1. Every fifth fraction (F5-F30), the GTV-T-F1 was adapted on the CBCT to create a GTV-T-Fx. Dose volume histograms were recalculated for every GTV-T-Fx, enabling to create lookup tables to predict the theoretical dosimetric advantage on common lung dose constraints.
  
  
  RESULTS
  The average GTV reduction was 42.1% (range 4.0-69.3%); 50.1% and 33.7% for the cCRT and sCRT patients, respectively. A linear relationship between GTV-T-F1 volume and absolute volume decrease was found for both groups. The mean V5, V20, V30 and mean lung dose increased by 0.8, 3.1, 5.2 and 3.4%, respectively. A larger increase (p < 0.05) was observed for peripheral tumors and cCRT. Lookup tables were generated.
  
  
  CONCLUSIONS
  ART offers the most beneficial dosimetric effects when performed around fraction 15, especially for patients with a large initial GTV-T treated by cCRT.
authors.affiliation: a Department of Radiation Oncology , Ghent University Hospital , Ghent , Belgium.|b Department of Radiation Oncology , Liège University Hospital , Liège , Belgium.
authors.forename: Patrick
authors.initials: P
authors.lastname: Berkovic
authors.affiliation: a Department of Radiation Oncology , Ghent University Hospital , Ghent , Belgium.
authors.forename: Leen
authors.initials: L
authors.lastname: Paelinck
authors.affiliation: a Department of Radiation Oncology , Ghent University Hospital , Ghent , Belgium.
authors.forename: Yolande
authors.initials: Y
authors.lastname: Lievens
authors.affiliation: b Department of Radiation Oncology , Liège University Hospital , Liège , Belgium.
authors.forename: Akos
authors.initials: A
authors.lastname: Gulyban
authors.affiliation: a Department of Radiation Oncology , Ghent University Hospital , Ghent , Belgium.
authors.forename: Bruno
authors.initials: B
authors.lastname: Goddeeris
authors.affiliation: a Department of Radiation Oncology , Ghent University Hospital , Ghent , Belgium.
authors.forename: Cristina
authors.initials: C
authors.lastname: Derie
authors.affiliation: a Department of Radiation Oncology , Ghent University Hospital , Ghent , Belgium.
authors.forename: Veerle
authors.initials: V
authors.lastname: Surmont
authors.affiliation: a Department of Radiation Oncology , Ghent University Hospital , Ghent , Belgium.
authors.forename: Wilfried
authors.initials: W
authors.lastname: De Neve
authors.affiliation: a Department of Radiation Oncology , Ghent University Hospital , Ghent , Belgium.
authors.forename: Katrien
authors.initials: K
authors.lastname: Vandecasteele
mesh_terms: D000368:Aged; D000369:Aged, 80 and over; D002289:Carcinoma, Non-Small-Cell Lung / Q000000981:diagnostic imaging / Q000532:radiotherapy*; D059248:Chemoradiotherapy / Q000379:methods*; D054893:Cone-Beam Computed Tomography; D019583:Dose Fractionation, Radiation; D005260:Female; D006801:Humans; D008175:Lung Neoplasms / Q000000981:diagnostic imaging / Q000532:radiotherapy*; D008297:Male; D008875:Middle Aged; D061089:Radiotherapy, Image-Guided / Q000379:methods*; D050397:Radiotherapy, Intensity-Modulated