title: Is diffusion-weighted MRI superior to FDG-PET or FDG-PET/CT in evaluating and predicting pathological response to preoperative neoadjuvant therapy in patients with rectal cancer?
abstract: OBJECTIVE
  This meta-analysis aimed to compare the diagnostic accuracy of diffusion-weighted magnetic resonance imaging (DW-MRI) and fluorodeoxyglucose-positron emission tomography (FDG-PET) or FDG-PET/computed tomography (CT) in evaluating and predicting pathological response to preoperative neoadjuvant chemoradiotherapy (NCRT) in patients with rectal cancer.
  
  
  METHODS
  A comprehensive literature research was conducted to identify the relevant studies for this meta-analysis. Combined sensitivity, specificity, positive (PPV) and negative predictive values (NPV) were calculated.
  
  
  RESULTS
  A total of 33 studies including 1564 patients met the inclusion criteria. The pooled sensitivity (81% [95% CI 74-86%] vs 85% [95% CI 75-91%]) and NPV (80% [95% CI 68-89%] vs 91% [95% CI 80-95%]) for FDG-PET or FDG-PET/CT were significantly lower than those for DW-MRI (P < 0.05). No differences were observed in pooled specificity and PPV between DW-MRI and FDG-PET or FDG-PET/CT. Further subgroup analyses showed that DW-MRI had higher sensitivity on adenocarcinomas alone than on those including mucinous-type adenocarcinomas (92% [95% CI 83-99%] vs 76% [95% CI 63-90%], P = 0.00).
  
  
  CONCLUSIONS
  DW-MRI is superior to FDG-PET or FDG-PET/CT in predicting and evaluating pathological responses to preoperative NCRT in patients with rectal cancer. However, its relatively low specificity and PPV limit its application in clinic, making it currently inappropriate to monitor such patients, especially those with mucinous-type rectal adenocarcinomas.
authors: Department of Radiology, Renji Hospital, Shanghai Jiaotong University School of Medicine, Shanghai, China.
authors: Yu Lai
authors: YL
authors: Li
authors: Lian Ming
authors: LM
authors: Wu
authors: Xiao Xi
authors: XX
authors: Chen
authors: Zachary
authors: Z
authors: Delproposto
authors: Jia Ni
authors: JN
authors: Hu
authors: Jian Rong
authors: JR
authors: Xu
mesh_terms: D059186:Chemoradiotherapy, Adjuvant / Q000379:methods; D038524:Diffusion Magnetic Resonance Imaging; D019788:Fluorodeoxyglucose F18; D006801:Humans; D064847:Multimodal Imaging / Q000379:methods; D020360:Neoadjuvant Therapy / Q000379:methods; D049268:Positron-Emission Tomography / Q000379:methods; D017594:Publication Bias; D019275:Radiopharmaceuticals; D012004:Rectal Neoplasms / Q000175:diagnosis* / Q000473:pathology / Q000628:therapy; D014057:Tomography, X-Ray Computed / Q000379:methods
chemical_list: D019275:Radiopharmaceuticals; D019788:Fluorodeoxyglucose F18
keywords: X-ray computed tomography; diffusion magnetic resonance imaging; neoadjuvant therapy; pathological response; positron-emission tomography; rectal neoplasm