title: Clinical utility of integrated positron emission tomography/computed tomography imaging in the clinical management and radiation treatment planning of locally advanced rectal cancer.
abstract: OBJECTIVE
  The role of 18F-fluorodeoxyglucose positron emission tomography-computed tomography (FDG-PET/CT) in the staging and radiation treatment planning of locally advanced rectal cancer is ill defined. We studied the role of integrated PET/CT in the staging, radiation treatment planning, and use as an imaging biomarker in rectal cancer patients undergoing multimodality treatment.
  
  
  METHODS
  Thirty-four consecutive patients with T3-4N0-2M0-1 rectal adenocarcinoma underwent FDG-PET/CT scanning for staging and radiation treatment planning. Planned clinical management was compared before and after the addition of PET/CT information. Three radiation oncologists independently delineated CT-based gross tumor volumes (GTVCT) using clinical information and CT imaging data, as well as gradient autosegmented PET/CT-based GTVs (GTVPETCT). The mean GTV, interobserver concordance index (CCI), and proximal and distal margins were compared. The maximal standardized uptake value (SUVmax), metabolic tumor volume (MTV), and dual-time point PET parameters were correlated with clinicopathologic endpoints.
  
  
  RESULTS
  Clinical management was altered by PET/CT in 18% (n = 6) of patients with clinical upstaging in 6 patients and radiation treatment planning altered in 5 patients. Of the 30 evaluable preoperative patients, the mean GTVPETCT was significantly smaller than the mean GTVCT volumes: 88.1 versus 102.8 cc (P = .03). PET/CT significantly increased interobserver CCI in contouring GTV compared with CT only-based contouring: 0.56 versus 0.38 (P < .001). The proximal and distal margins were altered by a mean of 0.4 ± 0.24 cm and -0.25 ± 0.18 cm, respectively. MTV was inversely associated with 2-year progression-free survival (PFS) and overall survival (OS): smaller MTVs (<33 cc) had superior 2-year PFS (86% vs 60%, P = .04) and OS (100% vs 45%, P < .01) compared with larger MTVs (>33 cc). SUVmax and dual-time point PET parameters did not correlate with any endpoints.
  
  
  CONCLUSIONS
  FDG-PET/CT imaging impacts overall clinical management and is useful in the radiation treatment planning of rectal cancer patients by decreasing interobserver variability in contouring target boost volumes. Pretreatment MTV may provide useful prognostic information and requires further study.
authors.affiliation: Department of Radiation Oncology, University of Pennsylvania, Abramson Cancer Center, Philadelphia, Pennsylvania.
authors.forename: Jonathan T
authors.initials: JT
authors.lastname: Whaley
authors.affiliation: Department of Radiation Oncology, University of Pennsylvania, Abramson Cancer Center, Philadelphia, Pennsylvania.
authors.forename: Annemarie T
authors.initials: AT
authors.lastname: Fernandes
authors.affiliation: Department of Radiation Oncology, University of Pennsylvania, Abramson Cancer Center, Philadelphia, Pennsylvania.
authors.forename: Robert
authors.initials: R
authors.lastname: Sackmann
authors.affiliation: Department of Radiation Oncology, University of Pennsylvania, Abramson Cancer Center, Philadelphia, Pennsylvania.
authors.forename: John P
authors.initials: JP
authors.lastname: Plastaras
authors.affiliation: Department of Radiation Oncology, University of Pennsylvania, Abramson Cancer Center, Philadelphia, Pennsylvania.
authors.forename: Boon-Keng
authors.initials: BK
authors.lastname: Teo
authors.affiliation: Department of Radiation Oncology, University of Pennsylvania, Abramson Cancer Center, Philadelphia, Pennsylvania.
authors.forename: Surbhi
authors.initials: S
authors.lastname: Grover
authors.affiliation: Division of Nuclear Medicine, Department of Radiology, University of Pennsylvania, Abramson Cancer Center, Philadelphia, Pennsylvania.
authors.forename: Rodolfo F
authors.initials: RF
authors.lastname: Perini
authors.affiliation: Department of Radiation Oncology, University of Pennsylvania, Abramson Cancer Center, Philadelphia, Pennsylvania.
authors.forename: James M
authors.initials: JM
authors.lastname: Metz
authors.affiliation: Division of Nuclear Medicine, Department of Radiology, University of Pennsylvania, Abramson Cancer Center, Philadelphia, Pennsylvania.
authors.forename: Daniel A
authors.initials: DA
authors.lastname: Pryma
authors.affiliation: Department of Radiation Oncology, University of Washington, Seattle, Washington. Electronic address: apisarn@uw.edu.
authors.forename: Smith
authors.initials: S
authors.lastname: Apisarnthanarax
mesh_terms: D000328:Adult; D000368:Aged; D005260:Female; D006801:Humans; D053208:Kaplan-Meier Estimate; D008297:Male; D008875:Middle Aged; D064847:Multimodal Imaging / Q000379:methods*; D049268:Positron-Emission Tomography / Q000379:methods*; D011880:Radiotherapy Planning, Computer-Assisted / Q000379:methods*; D012004:Rectal Neoplasms / Q000175:diagnosis* / Q000000981:diagnostic imaging / Q000401:mortality / Q000532:radiotherapy*; D012189:Retrospective Studies; D014057:Tomography, X-Ray Computed / Q000379:methods*