title: Use of pretreatment metabolic tumour volumes to predict the outcome of pharyngeal cancer treated by definitive radiotherapy.
abstract: OBJECTIVE
  The aim of the study was to investigate the predictive role of pretreatment metabolic volume (MTV) in pharyngeal cancer (PC) patients treated with definitive (chemo) radiotherapy.
  
  
  METHODS
  This retrospective analysis enrolled 64 patients with PC treated with (chemo) radiotherapy. All patients received pretreatment fluorodeoxyglucose (FDG) positron emission tomography (PET)/CT. Four PET segmentation methods were used, namely applying an isocontour at a standardized uptake value (SUV) of either 2.5 or 3.0 (MTV2.5 and MTV3.0) or using fixed thresholds of either 40 or 50 % (MTV40 %, MTV50 %) of the maximum intratumoural FDG activity. Disease-free survival (DFS) and primary relapse-free survival (PRFS) were examined according to cutoffs of the median values for each MTV and the gross tumour volume (GTVp). Independent prognosticators were identified by Cox regression analysis.
  
  
  RESULTS
  With a median follow-up of 24 months, 19 patients died, and 26 patients experienced tumour relapse at primary sites. Multivariate analysis of the DFS showed that MTV2.5 > 13.6 ml was the only predictor of relapse [p = 0.011, hazard ratio = 2.69, 95 % confidence interval (CI) 1.25-5.76]. The independent predictor for PRFS was MTV2.5 > 13.6 ml (p = 0.003, hazard ratio = 3.76, 95 % CI 1.57-8.92), whereas GTVp > 15.5 ml had a marginal impact on PRFS (p = 0.06, hazard ratio = 3.54, 95 % CI 0.97-11.85). Patients having tumours with MTV2.5 > 13.6 ml had a significantly inferior 2-year PRFS compared with patients who had lower MTV2.5 tumours (39 vs 72 %, respectively, p = 0.001).
  
  
  CONCLUSIONS
  For PC patients treated with definitive (chemo)radiotherapy, pretreatment MTV2.5 volume achieved the best predictive value for primary recurrence, and the same value was also a prognosticator for DFS.
authors.affiliation: Department of Nuclear Medicine and PET Center, China Medical University Hospital, Taichung, Taiwan. d10040@mail.cmuh.org.tw
authors.forename: Chia-Hung
authors.initials: CH
authors.lastname: Kao
authors.forename: Shih-Chieh
authors.initials: SC
authors.lastname: Lin
authors.forename: Te-Chun
authors.initials: TC
authors.lastname: Hsieh
authors.forename: Kuo-Yang
authors.initials: KY
authors.lastname: Yen
authors.forename: Shih-Neng
authors.initials: SN
authors.lastname: Yang
authors.forename: Yao-Ching
authors.initials: YC
authors.lastname: Wang
authors.forename: Ji-An
authors.initials: JA
authors.lastname: Liang
authors.forename: Chun-Hung
authors.initials: CH
authors.lastname: Hua
authors.forename: Shang-Wen
authors.initials: SW
authors.lastname: Chen
mesh_terms: D000328:Adult; D000368:Aged; D005260:Female; D006801:Humans; D008297:Male; D008875:Middle Aged; D010610:Pharyngeal Neoplasms / Q000175:diagnosis / Q000378:metabolism / Q000473:pathology* / Q000532:radiotherapy*; D011379:Prognosis; D012189:Retrospective Studies; D016896:Treatment Outcome; D047368:Tumor Burden / Q000528:radiation effects