title: Comparison of PET metabolic indices for the early assessment of tumour response in metastatic colorectal cancer patients treated by polychemotherapy.
abstract: OBJECTIVE
  To compare the performance of eight metabolic indices for the early assessment of tumour response in patients with metastatic colorectal cancer (mCRC) treated with chemotherapy.
  
  
  METHODS
  Forty patients with advanced mCRC underwent two FDG PET/CT scans, at baseline and on day 14 after chemotherapy initiation. For each lesion, eight metabolic indices were calculated: four standardized uptake values (SUV) without correction for the partial volume effect (PVE), two SUV with correction for PVE, a metabolic volume (MV) and a total lesion glycolysis (TLG). The relative change in each index between the two scans was calculated for each lesion. Lesions were also classified as responding and nonresponding lesions using the Response Evaluation Criteria In Solid Tumours (RECIST) 1.0 measured by contrast-enhanced CT at baseline and 6-8 weeks after starting therapy. Bland-Altman analyses were performed to compare the various indices. Based on the RECIST classification, ROC analyses were used to determine how accurately the indices predicted lesion response to therapy later seen with RECIST.
  
  
  RESULTS
  RECIST showed 27 responding and 74 nonresponding lesions. Bland-Altman analyses showed that the four SUV indices uncorrected for PVE could not be used interchangeably, nor could the two SUV corrected for PVE. The areas under the ROC curves (AUC) were not significantly different between the SUV indices not corrected for PVE. The mean SUV change in a lesion better predicted lesion response without than with PVE correction. The AUC was significantly higher for SUV uncorrected for PVE than for the MV, but change in MV provided some information regarding the lesion response to therapy (AUC >0.5).
  
  
  CONCLUSIONS
  In these mCRC patients, all SUV uncorrected for PVE accurately predicted the tumour response on day 14 after starting therapy as assessed 4 to 6 weeks later (i.e. 6 to 8 weeks after therapy initiation) using the RECIST criteria. Neither correcting SUV for PVE nor measuring TLG improved the assessment of tumour response compared to SUV uncorrected for PVE. The change in MV was the least accurate index for predicting tumour response.
authors.affiliation: IMNC UMR 8165 CNRS - Paris 7 and Paris 11 Universities, Building 440, Orsay Campus, 91406 Orsay Cedex, France. maisonobe@imnc.in2p3.fr
authors.forename: Jacques-Antoine
authors.initials: JA
authors.lastname: Maisonobe
authors.forename: Camilo A
authors.initials: CA
authors.lastname: Garcia
authors.forename: Hatem
authors.initials: H
authors.lastname: Necib
authors.forename: Bruno
authors.initials: B
authors.lastname: Vanderlinden
authors.forename: Alain
authors.initials: A
authors.lastname: Hendlisz
authors.forename: Patrick
authors.initials: P
authors.lastname: Flamen
authors.forename: Irène
authors.initials: I
authors.lastname: Buvat
mesh_terms: D000293:Adolescent; D000328:Adult; D000368:Aged; D000369:Aged, 80 and over; D000971:Antineoplastic Combined Chemotherapy Protocols / Q000627:therapeutic use; D015179:Colorectal Neoplasms / Q000188:drug therapy* / Q000473:pathology*; D003287:Contrast Media / Q000494:pharmacology; D004359:Drug Therapy, Combination / Q000379:methods; D005260:Female; D006019:Glycolysis; D006801:Humans; D008297:Male; D008875:Middle Aged; D015233:Models, Statistical; D009362:Neoplasm Metastasis; D049268:Positron-Emission Tomography / Q000379:methods*; D012372:ROC Curve; D015203:Reproducibility of Results
chemical_list: D003287:Contrast Media