title: Total 18F-dopa PET tumour uptake reflects metabolic endocrine tumour activity in patients with a carcinoid tumour.
abstract: OBJECTIVE
  Positron emission tomography (PET) using 6-[18F]fluoro-L-dihydroxyphenylalanine (18F-dopa) has an excellent sensitivity to detect carcinoid tumour lesions. 18F-dopa tumour uptake and the levels of biochemical tumour markers are mediated by tumour endocrine metabolic activity. We evaluated whether total 18F-dopa tumour uptake on PET, defined as whole-body metabolic tumour burden (WBMTB), reflects tumour load per patient, as measured with tumour markers.
  
  
  METHODS
  Seventy-seven consecutive carcinoid patients who underwent an 18F-dopa PET scan in two previously published studies were analysed. For all tumour lesions mean standardised uptake values (SUVs) at 40% of the maximal SUV and tumour volume on 18F-dopa PET were determined and multiplied to calculate a metabolic burden per lesion. WBMTB was the sum of the metabolic burden of all individual lesions per patient. The 24-h urinary serotonin, urine and plasma 5-hydroxindoleacetic acid (5-HIAA), catecholamines (nor)epinephrine, dopamine and their metabolites, measured in urine and plasma, and serum chromogranin A served as tumour markers.
  
  
  RESULTS
  All but 1 were evaluable for WBMTB; 74 patients had metastatic disease. 18F-dopa PET detected 979 lesions. SUVmax on 18F-dopa PET varied up to 29-fold between individual lesions within the same patients. WBMTB correlated with urinary serotonin (r=0.51) and urinary and plasma 5-HIAA (r=0.78 and 0.66). WBMTB also correlated with urinary norepinephrine, epinephrine, dopamine and plasma dopamine, but not with serum chromogranin A.
  
  
  CONCLUSIONS
  Tumour load per patient measured with 18F-dopa PET correlates with tumour markers of the serotonin and catecholamine pathway in urine and plasma in carcinoid patients, reflecting metabolic tumour activity.
authors.affiliation: Department of Medical Oncology, University Medical Centre Groningen, P.O. Box 30.001, 9700 RB, Groningen, The Netherlands.
authors.forename: Helle-Brit
authors.initials: HB
authors.lastname: Fiebrich
authors.forename: Johan R
authors.initials: JR
authors.lastname: de Jong
authors.forename: Ido P
authors.initials: IP
authors.lastname: Kema
authors.forename: Klaas Pieter
authors.initials: KP
authors.lastname: Koopmans
authors.forename: Wim
authors.initials: W
authors.lastname: Sluiter
authors.forename: Rudi A J O
authors.initials: RA
authors.lastname: Dierckx
authors.forename: Annemiek M
authors.initials: AM
authors.lastname: Walenkamp
authors.forename: Thera P
authors.initials: TP
authors.lastname: Links
authors.forename: Adrienne H
authors.initials: AH
authors.lastname: Brouwers
authors.forename: Elisabeth G E
authors.initials: EG
authors.lastname: de Vries
mesh_terms: D000293:Adolescent; D000328:Adult; D000368:Aged; D001692:Biological Transport; D002276:Carcinoid Tumor / Q000000981:diagnostic imaging* / Q000378:metabolism*; D004295:Dihydroxyphenylalanine / Q000031:analogs & derivatives* / Q000378:metabolism; D004701:Endocrine Gland Neoplasms / Q000000981:diagnostic imaging* / Q000378:metabolism*; D005260:Female; D006801:Humans; D007090:Image Interpretation, Computer-Assisted; D008297:Male; D008875:Middle Aged; D049268:Positron-Emission Tomography; D012189:Retrospective Studies; D055815:Young Adult
chemical_list: C043437:fluorodopa F 18; D004295:Dihydroxyphenylalanine