title: Dose painting by contours versus dose painting by numbers for stage II/III lung cancer: practical implications of using a broad or sharp brush.
abstract: OBJECTIVE
  Local recurrence rates are high in patients with locally advanced NSCLC treated with 60 to 66 Gy in 2 Gy fractions. It is hypothesised that boosting volumes with high SUV on the pre-treatment FDG-PET scan potentially increases local control while maintaining acceptable toxicity levels. We compared two approaches: threshold-based dose painting by contours (DPBC) with voxel-based dose painting by numbers (DPBN).
  
  
  METHODS
  Two dose painted plans were generated for 10 stage II/III NSCLC patients with 66 Gy at 2-Gy fractions to the entire PTV and a boost dose to the high SUV areas within the primary GTV. DPBC aims for a uniform boost dose at the volume encompassing the SUV 50%-region (GTV(boost)). DPBN aims for a linear relationship between the boost dose to a voxel and the underlying SUV. For both approaches the boost dose was escalated up to 130 Gy (in 33 fractions) or until the dose limiting constraint of an organ at risk was met.
  
  
  RESULTS
  For three patients (with relatively small peripheral tumours) the dose within the GTV could be boosted to 130 Gy using both strategies. For the remaining patients the boost dose was confined by a critical structure (mediastinal structures in six patients, lungs in one patient). In general the amount of large brush DPBC boosting is limited whenever the GTV(boost) is close to any serial risk organ. In contrast, small brush DPBN inherently boosts at a voxel-by-voxel basis allowing significant higher dose values to high SUV voxels more distant from the organs at risk. We found that the biological SUV gradients are reasonably congruent with the dose gradients that standard linear accelerators can deliver.
  
  
  CONCLUSIONS
  Both large brush DPBC and sharp brush DPBN techniques can be used to considerably boost the dose to the FDG avid regions. However, significantly higher boost levels can be obtained using sharp brush DPBN although sometimes at the cost of a less increased dose to the low SUV regions.
authors.affiliation: Radiotherapy Department, Catharina Hospital Eindhoven, The Netherlands. g.j.meijer@umcutrecht.nl
authors.forename: Gert
authors.initials: G
authors.lastname: Meijer
authors.forename: Jacco
authors.initials: J
authors.lastname: Steenhuijsen
authors.forename: Matthieu
authors.initials: M
authors.lastname: Bal
authors.forename: Katrien
authors.initials: K
authors.lastname: De Jaeger
authors.forename: Danny
authors.initials: D
authors.lastname: Schuring
authors.forename: Jacqueline
authors.initials: J
authors.lastname: Theuws
mesh_terms: D001917:Brachial Plexus / Q000528:radiation effects; D002289:Carcinoma, Non-Small-Cell Lung / Q000000981:diagnostic imaging* / Q000532:radiotherapy*; D019583:Dose Fractionation, Radiation; D004307:Dose-Response Relationship, Radiation; D004947:Esophagus / Q000528:radiation effects; D019788:Fluorodeoxyglucose F18; D006321:Heart / Q000528:radiation effects; D006801:Humans; D008168:Lung / Q000528:radiation effects; D008175:Lung Neoplasms / Q000000981:diagnostic imaging* / Q000473:pathology / Q000532:radiotherapy*; D008207:Lymphatic Metastasis; D049268:Positron-Emission Tomography / Q000379:methods*; D011874:Radiometry / Q000379:methods; D019275:Radiopharmaceuticals; D011879:Radiotherapy Dosage; D011880:Radiotherapy Planning, Computer-Assisted / Q000379:methods*; D013116:Spinal Cord / Q000528:radiation effects; D016896:Treatment Outcome
chemical_list: D019275:Radiopharmaceuticals; D019788:Fluorodeoxyglucose F18