title: Assessing local progression after stereotactic body radiation therapy for unresectable pancreatic adenocarcinoma: CT versus PET.
abstract: OBJECTIVE
  Evaluation of local tumor progression (LP) has typically been defined by contrast-enhanced computed tomography (CT) imaging after stereotactic body radiation therapy (SBRT) for locally advanced pancreatic cancer (PDAC). The purpose of this study is to determine the benefit of adding 18F-fluorodeoxyglucose-positron emission tomography (FDG-PET) imaging to CT for LP assessment of PDAC after SBRT.
  
  
  METHODS
  We retrospectively reviewed pretreatment, follow-up images, and outcomes of all patients treated with definitive SBRT for unresectable PDAC between December 2002 and December 2015 at our institution. For each patient, we independently analyzed LP both by CT and by FDG-PET criteria, using the Response Evaluation Criteria In Solid Tumors version 1.1 and the FDG-PET Response Evaluation Criteria In Solid Tumors version 1.0, respectively.
  
  
  RESULTS
  Among 206 patients treated with definitive SBRT for unresectable PDAC, we identified 30 with LP on follow-up. Four did not undergo follow-up FDG-PET. Median time to LP after SBRT was 7.5 months (range, 2-25 months). Of the 26 patients with LP who had follow-up FDG-PET, 21 were diagnosed by FDG-PET (80.7%), 14 by CT (53.8%), and 9 by both FDG-PET and CT (34.6%). Use of CT alone revealed only 53.8% of cases of LP detected when FDG-PET and CT were combined. The cumulative incidence of LP, based on competing risk of death, at 1 and 2 years after SBRT was 9.6% and 16.7% by CT and 11% and 29.1% by FDG-PET, respectively.
  
  
  CONCLUSIONS
  FDG-PET increases the chance of detecting LP of unresectable PDAC after SBRT and can have an important impact on reported outcomes. We recommend obtaining FDG-PET to assess treatment response when evaluating efficacy of SBRT and taking its use into account when comparing clinical data.
authors.affiliation: Radiation Oncology Department, Stanford University School of Medicine, Stanford, California.
authors.forename: Diego A S
authors.initials: DAS
authors.lastname: Toesca
authors.affiliation: Radiation Oncology Department, Stanford University School of Medicine, Stanford, California.
authors.forename: Erqi L
authors.initials: EL
authors.lastname: Pollom
authors.affiliation: Radiology Department, Stanford University School of Medicine, Stanford, California.
authors.forename: Peter D
authors.initials: PD
authors.lastname: Poullos
authors.affiliation: Nuclear Medicine Department, Stanford University School of Medicine, Stanford, California.
authors.forename: Lesley
authors.initials: L
authors.lastname: Flynt
authors.affiliation: Radiation Oncology Department, Stanford University School of Medicine, Stanford, California.
authors.forename: Yi
authors.initials: Y
authors.lastname: Cui
authors.affiliation: Nuclear Medicine Department, Stanford University School of Medicine, Stanford, California.
authors.forename: Andrew
authors.initials: A
authors.lastname: Quon
authors.affiliation: Radiation Oncology Department, Stanford University School of Medicine, Stanford, California.
authors.forename: Rie
authors.initials: R
authors.lastname: von Eyben
authors.affiliation: Radiation Oncology Department, Stanford University School of Medicine, Stanford, California.
authors.forename: Albert C
authors.initials: AC
authors.lastname: Koong
authors.affiliation: Radiation Oncology Department, Stanford University School of Medicine, Stanford, California. Electronic address: dtchang@stanford.edu.
authors.forename: Daniel T
authors.initials: DT
authors.lastname: Chang
mesh_terms: D000328:Adult; D000368:Aged; D000369:Aged, 80 and over; D021441:Carcinoma, Pancreatic Ductal / Q000000981:diagnostic imaging* / Q000532:radiotherapy; D018450:Disease Progression; D005260:Female; D019788:Fluorodeoxyglucose F18; D005500:Follow-Up Studies; D006801:Humans; D008297:Male; D008875:Middle Aged; D010190:Pancreatic Neoplasms / Q000000981:diagnostic imaging* / Q000532:radiotherapy; D049268:Positron-Emission Tomography / Q000379:methods*; D019275:Radiopharmaceuticals; D016634:Radiosurgery; D012189:Retrospective Studies; D014057:Tomography, X-Ray Computed / Q000379:methods*; D016896:Treatment Outcome
chemical_list: D019275:Radiopharmaceuticals; D019788:Fluorodeoxyglucose F18