title: Correlation between therapy response assessment using FDG PET/CT and histopathologic tumor regression grade in hepatic metastasis of colorectal carcinoma after neoadjuvant therapy.
abstract: OBJECTIVE
  To evaluate the correlation between change in FDG uptake before and after chemotherapy in hepatic metastases of colorectal carcinoma (HCRC) and a histopathologic tumor regression grade (TRG).
  
  
  METHODS
  In patients with HCRC, PET/CT data prior to hepatic surgery were retrospectively analyzed under an IRB waiver. The maximum standard uptake value (SUVmax) was measured before and after chemotherapy. The relative change of FDG activity in the identified lesions was calculated (dSUV). Histopathological specimens of resected metastases were graded on a 5-score TRG scale. A TRG of 1-3 was rated as a responding to therapy, whereas TRG 4-5 were regarded as non-responding lesions.
  
  
  RESULTS
  31 lesions were identified in 23 patients. Mean SUVmax before and after therapy was 6.9 ± 3.7 and 3.5 ± 1.8, respectively. The area under the receiver operator characteristic curve revealed a conclusive correlation between TRG and dSUV (AUC 0.773; 95% confidence interval 0.599-0.946) with a cut off at 41% decrease in FDG activity yielding a sensitivity and specificity of 72 and 75%, respectively.
  
  
  CONCLUSIONS
  A relative change in FDG activity (dSUV) of more than 41% decrease correlated significantly with histopathological tumor regression and might be a prognostic tool for response to chemotherapy in HCRC.
authors.affiliation: Division of Nuclear Medicine, Department Medical Radiology, University Hospital Zurich, Ramistr. 100, 8091, Zurich, Switzerland. irene.burger@usz.ch
authors.forename: Irene A
authors.initials: IA
authors.lastname: Burger
authors.forename: Esther I
authors.initials: EI
authors.lastname: Schwarz
authors.forename: Andrei
authors.initials: A
authors.lastname: Samarin
authors.forename: Stefan
authors.initials: S
authors.lastname: Breitenstein
authors.forename: Achim
authors.initials: A
authors.lastname: Weber
authors.forename: Thomas F
authors.initials: TF
authors.lastname: Hany
mesh_terms: D001692:Biological Transport; D015179:Colorectal Neoplasms / Q000473:pathology*; D005260:Female; D019788:Fluorodeoxyglucose F18 / Q000378:metabolism; D006801:Humans; D008113:Liver Neoplasms / Q000000981:diagnostic imaging / Q000473:pathology / Q000556:secondary* / Q000628:therapy*; D008297:Male; D008875:Middle Aged; D064847:Multimodal Imaging; D020360:Neoadjuvant Therapy; D060787:Neoplasm Grading; D049268:Positron-Emission Tomography; D012372:ROC Curve; D014057:Tomography, X-Ray Computed; D016896:Treatment Outcome
chemical_list: D019788:Fluorodeoxyglucose F18