title: Evaluation for local failure by 18F-FDG PET/CT in comparison with CT findings after stereotactic body radiotherapy (SBRT) for localized non-small-cell lung cancer.
abstract: OBJECTIVE
  Stereotactic body radiotherapy (SBRT) is the standard care for medically inoperable early non-small-cell lung cancer (NSCLC). However, it can be difficult to differentiate local recurrence from non-recurrence radiation-induced lung opacity. We retrospectively assessed (18)F-FDG PET/CT to detect local recurrence after SBRT for NSCLC.
  
  
  METHODS
  Between 2005 and 2011, 273 NSCLCs in 257 patients were treated with SBRT. Prescribed doses were 50Gy and 40Gy per 5 fractions for peripheral and central lesions, respectively. Tri-monthly follow-up CT scans were acquired. (18)F-FDG PET/CT scans were scheduled for screening at one year after SBRT or when recurrence was highly suspected. The dual-time-point maximum standardized uptake values (SUVmaxs) and their retention indexes (RIs) were obtained.
  
  
  RESULTS
  A total of 214 (18)F-FDG PET/CT scans were obtained for 164 localized NSCLC tumors in 154 patients. The median follow-up period was 24.9 months (range: 6.3-72.1). Among these, 21 scans of 17 tumors were diagnosed as local recurrence. The median SUVmaxs on early and late images of recurrence and their RI were 5.0 (range: 3.2-10.7), 6.3 (range: 4.2-13.4), and 0.20 (range; 0-0.41), respectively. These were significantly higher than the respective values of non-recurrence images of 1.8 (range: 0.5-4.6), 1.7 (range: 0.5-6.1), and 0.00 (range: -0.37-0.41) (all p<0.05). For SUVmaxs on early and late images, optimal thresholds were identified as 3.2 and 4.2. Using each threshold, the sensitivity and specificity were 100% and 96-98%, respectively. CT findings were classified into ground-glass opacity (N=9), scar or fibrotic change (N=96), consolidation with air-bronchogram (N=34), consolidation only (N=22), and nodule (N=17); the respective numbers of recurrence were 0, 0, 1, 3, and 17.
  
  
  CONCLUSIONS
  SUVmaxs of (18)F-FDG PET/CT could detect local recurrence after SBRT for localized NSCLC. In contrast, CT scan results had a limited ability to diagnose local recurrence.
authors.affiliation: Department of Radiology, Ofuna Chuo Hospital, Japan.
authors.forename: Atsuya
authors.initials: A
authors.lastname: Takeda
authors.forename: Etsuo
authors.initials: E
authors.lastname: Kunieda
authors.forename: Hirofumi
authors.initials: H
authors.lastname: Fujii
authors.forename: Noriko
authors.initials: N
authors.lastname: Yokosuka
authors.forename: Yousuke
authors.initials: Y
authors.lastname: Aoki
authors.forename: Yoshikazu
authors.initials: Y
authors.lastname: Oooka
authors.forename: Yohei
authors.initials: Y
authors.lastname: Oku
authors.forename: Toshio
authors.initials: T
authors.lastname: Ohashi
authors.forename: Naoko
authors.initials: N
authors.lastname: Sanuki
authors.forename: Tomikazu
authors.initials: T
authors.lastname: Mizuno
authors.forename: Yukihiko
authors.initials: Y
authors.lastname: Ozawa
mesh_terms: D000368:Aged; D000369:Aged, 80 and over; D002289:Carcinoma, Non-Small-Cell Lung / Q000175:diagnosis* / Q000473:pathology / Q000532:radiotherapy; D003951:Diagnostic Errors / Q000517:prevention & control*; D019788:Fluorodeoxyglucose F18 / Q000378:metabolism; D005500:Follow-Up Studies; D006801:Humans; D008168:Lung / Q000000981:diagnostic imaging / Q000473:pathology*; D008175:Lung Neoplasms / Q000175:diagnosis* / Q000473:pathology / Q000532:radiotherapy; D008875:Middle Aged; D064847:Multimodal Imaging / Q000379:methods; D009367:Neoplasm Staging; D049268:Positron-Emission Tomography; D016634:Radiosurgery / Q000379:methods*; D012008:Recurrence; D014057:Tomography, X-Ray Computed / Q000379:methods
chemical_list: D019788:Fluorodeoxyglucose F18