title: Pre-Chemoradiotherapy FDG PET/CT cannot Identify Residual Metabolically-Active Volumes within Individual Esophageal Tumors.
abstract: OBJECTIVE
  To study whether subvolumes with a high pre-chemoradiotherapy (CRT) FDG uptake could identify residual metabolically-active volumes (MAVs) post-CRT within individual esophageal tumors. Accurate identification will allow simultaneous integrated boost to these subvolumes at higher risk to improve clinical outcomes.
  
  
  METHODS
  Twenty patients with esophageal cancer were treated with CRT plus surgery and underwent FDG PET/CT scans before and after CRT. The two scans were rigidly registered. Seven MAVs pre-CRT and four MAVs post-CRT within a tumor were defined with various SUV thresholds. The similarity and proximity between the MAVs pre-CRT and post-CRT were quantified with three metrics: fraction of post-CRT MAV included in pre-CRT MAV, volume overlap and centroid distance.
  
  
  RESULTS
  Eight patients had no residual MAV. Six patients had local residual MAV (SUV ≥2.5 post-CRT) within or adjoining the original MAV (SUV ≥2.5 pre-CRT). On average, less than 65% of any post-CRT MAVs was included in any pre-CRT MAVs, with a low volume overlap <45%, and large centroid distance >8.6 mm. In general, subvolumes with higher FDG-uptake pre-CRT or post-CRT had lower volume overlap and larger centroid distance. Six patients had new distant MAVs that were determined to be inflammation from radiation therapy.
  
  
  CONCLUSIONS
  Pre-CRT PET/CT cannot reliably identify the residual MAVs within individual esophageal tumors. Simultaneous integrated boost to subvolumes with high FDG uptake pre-CRT may not be feasible.
authors.affiliation: Department of Radiation Oncology, University of Maryland School of Medicine, Baltimore, USA.
authors.forename: W
authors.initials: W
authors.lastname: Lu
authors.affiliation: Department of Radiation Oncology, University of Maryland School of Medicine, Baltimore, USA ; Department of Control Science and Engineering, Huazhong University of Science and Technology, Wuhan, China.
authors.forename: S
authors.initials: S
authors.lastname: Tan
authors.affiliation: Department of Diagnostic Radiology and Nuclear Medicine, University of Maryland School of Medicine, Baltimore, USA.
authors.forename: W
authors.initials: W
authors.lastname: Chen
authors.affiliation: Department of Diagnostic Radiology and Nuclear Medicine, University of Maryland School of Medicine, Baltimore, USA.
authors.forename: S
authors.initials: S
authors.lastname: Kligerman
authors.affiliation: Department of Radiation Oncology, University of Maryland School of Medicine, Baltimore, USA.
authors.forename: S J
authors.initials: SJ
authors.lastname: Feigenberg
authors.affiliation: Department of Radiation Oncology, University of Maryland School of Medicine, Baltimore, USA.
authors.forename: H
authors.initials: H
authors.lastname: Zhang
authors.affiliation: Department of Radiation Oncology, University of Maryland School of Medicine, Baltimore, USA.
authors.forename: M
authors.initials: M
authors.lastname: Suntharalingam
authors.affiliation: Department of Radiation Oncology, University of Maryland School of Medicine, Baltimore, USA ; Department of Radiation Oncology, Yeungnam University College of Medicine, Daegu, South Korea.
authors.forename: M
authors.initials: M
authors.lastname: Kang
authors.affiliation: Department of Radiation Oncology, University of Maryland School of Medicine, Baltimore, USA.
authors.forename: W D
authors.initials: WD
authors.lastname: D'Souza
keywords: 18F-FDG PET/CT; Esophageal cancer; Radiation therapy