title: Optimal gross tumor volume definition in lung-sparing intensity modulated radiotherapy for pleural mesothelioma: an in silico study.
abstract: BACKGROUND
  The gross tumor volume (GTV) definition for malignant pleural mesothelioma (MPM) is ill-defined. We therefore investigated which imaging modality is optimal: computed tomography (CT) with intravenous contrast (IVC), positron emission tomography-CT (PET/CT) or magnetic resonance imaging (MRI).
  
  
  METHODS
  Sixteen consecutive patients with untreated stage I-IV MPM were included. Patients with prior pleurodesis were excluded. CT with IVC, 18FDG-PET/CT and MRI (T2 and contrast-enhanced T1) were obtained. CT was rigidly co-registered with PET/CT and with MRI. Three sets of pleural GTVs were defined: GTVCT, GTVCT+PET/CTand GTVCT+MRI. Quantitative and qualitative evaluations of the contoured GTVs were performed.
  
  
  RESULTS
  Compared to CT-based GTV definition, PET/CT identified additional tumor sites (defined as either separate nodules or greater extent of a known tumor) in 12/16 patients. Compared to either CT or PET/CT, MRI identified additional tumor sites in 15/16 patients (p = .7). The mean GTVCT, GTVCT+PET/CTand GTVCT+MRI[±standard deviation (SD)] were 630.1 cm3(±302.81), 640.23 cm3(±302.83) and 660.8 cm3(±290.8), respectively. Differences in mean volumes were not significant. The mean Jaccard Index was significantly lower in MRI-based contours versus all the others.
  
  
  CONCLUSIONS
  As MRI identified additional pleural disease sites in the majority of patients, it may play a role in optimal target volume definition.
authors.affiliation: a Department of Oncology, Experimental Radiation Oncology , KU Leuven-University of Leuven , Leuven , Belgium.
authors.forename: Angela
authors.initials: A
authors.lastname: Botticella
authors.affiliation: a Department of Oncology, Experimental Radiation Oncology , KU Leuven-University of Leuven , Leuven , Belgium.
authors.forename: Gilles
authors.initials: G
authors.lastname: Defraene
authors.affiliation: b Respiratory Diseases/Respiratory Oncology Unit , KU Leuven-University of Leuven, University Hospitals Leuven , Leuven , Belgium.
authors.forename: Kristiaan
authors.initials: K
authors.lastname: Nackaerts
authors.affiliation: c Department Imaging and Pathology, Nuclear Medicine and Molecular Imaging , KU Leuven-University of Leuven, University Hospitals Leuven , Leuven , Belgium.
authors.forename: Christophe M
authors.initials: CM
authors.lastname: Deroose
authors.affiliation: d Radiology Department , University Hospitals Leuven , Leuven , Belgium.
authors.forename: Johan
authors.initials: J
authors.lastname: Coolen
authors.affiliation: e Department of Thoracic Surgery , University Hospitals Leuven , Leuven , Belgium.
authors.forename: Philippe
authors.initials: P
authors.lastname: Nafteux
authors.affiliation: f Department of Radiation Oncology , KU Leuven-University of Leuven, University Hospitals Leuven , Leuven , Belgium.
authors.forename: Stephanie
authors.initials: S
authors.lastname: Peeters
authors.affiliation: g Department of Oncology, Radiation Oncology , University of Turin , Turin , Italy.
authors.forename: Umberto
authors.initials: U
authors.lastname: Ricardi
authors.affiliation: f Department of Radiation Oncology , KU Leuven-University of Leuven, University Hospitals Leuven , Leuven , Belgium.|h GROW-School for Oncology and Developmental Biology, Department of Radiation Oncology (MAASTRO clinic) , Maastricht University Medical Center , Maastricht , The Netherlands.
authors.forename: Dirk
authors.initials: D
authors.lastname: De Ruysscher
mesh_terms: D000368:Aged; D003198:Computer Simulation; D005260:Female; D019788:Fluorodeoxyglucose F18; D005500:Follow-Up Studies; D006801:Humans; D008168:Lung / Q000528:radiation effects*; D008175:Lung Neoplasms / Q000378:metabolism / Q000473:pathology* / Q000532:radiotherapy; D008279:Magnetic Resonance Imaging; D008297:Male; D008654:Mesothelioma / Q000378:metabolism / Q000473:pathology* / Q000532:radiotherapy; D000086002:Mesothelioma, Malignant; D064847:Multimodal Imaging / Q000379:methods*; D009367:Neoplasm Staging; D059351:Organ Sparing Treatments; D010997:Pleural Neoplasms / Q000378:metabolism / Q000473:pathology* / Q000532:radiotherapy; D000072078:Positron Emission Tomography Computed Tomography; D011379:Prognosis; D011446:Prospective Studies; D019275:Radiopharmaceuticals; D011880:Radiotherapy Planning, Computer-Assisted; D050397:Radiotherapy, Intensity-Modulated / Q000379:methods*; D012189:Retrospective Studies; D015996:Survival Rate; D047368:Tumor Burden
chemical_list: D019275:Radiopharmaceuticals; D019788:Fluorodeoxyglucose F18