title: Comparison of CT and integrated PET-CT based radiation therapy planning in patients with malignant pleural mesothelioma.
abstract: BACKGROUND
  When combined with adequate tumoricidal doses, accurate target volume delineation remains to be the one of the most important predictive factors for radiotherapy (RT) success in locally advanced or medically inoperable malignant pleural mesothelioma (MPM) patients. Recently, 18-fluorodeoxyglucose positron emission tomography (PET) has demonstrated significant improvements in diagnosis and accurate staging of MPM. However, role of additional PET data has not been studied in RT planning (RTP) of patients with inoperable MPM or in those who refuse surgery. Therefore, we planned to compare CT with co-registered PET-CT as the basis for delineating target volumes in these patients group.
  
  
  METHODS
  Retrospectively, the CT and co-registered PET-CT data of 13 patients with histologically proven MPM were utilized to delineate target volumes separately. For each patient, target volumes (gross tumor volume [GTV], clinical target volume [CTV], and planning target volume [PTV]) were defined using the CT and PET-CT fusion data sets. The PTV was measured in two ways: PTV1 was CTV plus a 1-cm margin, and PTV2 was GTV plus a 1-cm margin. We analyzed differences in target volumes.
  
  
  RESULTS
  In 12 of 13 patients, compared to CT-based delineation, PET-CT-based delineation resulted in a statistically significant decrease in the mean GTV, CTV, PTV1, and PTV2. In these 12 patients, mean GTV decreased by 47.1% +/- 28.4%, mean CTV decreased by 38.7% +/- 24.7%, mean PTV1 decreased by 31.1% +/- 23.1%, and mean PTV2 decreased by 40.0% +/- 24.0%. In 4 of 13 patients, hilar lymph nodes were identified by PET-CT that was not identified by CT alone, changing the nodal status of tumor staging in those patients.
  
  
  CONCLUSIONS
  This study demonstrated the usefulness of PET-CT-based target volume delineation in patients with MPM. Co-registration of PET and CT information reduces the likelihood of geographic misses, and additionally, significant reductions observed in target volumes may potentially allow escalation of RT dose beyond conventional limits potential clinical benefits in tumor control rates, which needs to be tested in future studies.
authors.affiliation: Department of Radiation Oncology, Baskent University Medical Faculty, Adana Medical and Research Center, Kisla Campus, Adana, Turkey. berrin_pehlivan@yahoo.com
authors.forename: Berrin
authors.initials: B
authors.lastname: Pehlivan
authors.forename: Erkan
authors.initials: E
authors.lastname: Topkan
authors.forename: Cem
authors.initials: C
authors.lastname: Onal
authors.forename: Gul Nihal
authors.initials: GN
authors.lastname: Nursal
authors.forename: Oznur
authors.initials: O
authors.lastname: Yuksel
authors.forename: Yemliha
authors.initials: Y
authors.lastname: Dolek
authors.forename: Melek Nur
authors.initials: MN
authors.lastname: Yavuz
authors.forename: Ali Aydin
authors.initials: AA
authors.lastname: Yavuz
mesh_terms: D000328:Adult; D000368:Aged; D005260:Female; D019788:Fluorodeoxyglucose F18; D006801:Humans; D008297:Male; D008654:Mesothelioma / Q000000981:diagnostic imaging*; D008875:Middle Aged; D010997:Pleural Neoplasms / Q000000981:diagnostic imaging*; D049268:Positron-Emission Tomography / Q000379:methods*; D019275:Radiopharmaceuticals; D011880:Radiotherapy Planning, Computer-Assisted / Q000379:methods*; D014057:Tomography, X-Ray Computed / Q000379:methods*
chemical_list: D019275:Radiopharmaceuticals; D019788:Fluorodeoxyglucose F18