title: PET with hydroxytryptophan as tracer in hormone-refractory prostatic adenocarcinoma: evaluation of decarboxylation in vivo.
abstract: Position emission tomography (PET) was performed on two patients with hormone-refractory prostatic adenocarcinoma in order to characterize the mechanism behind an earlier observed increased uptake of tracer hydroxytryptophan (5-HTP) in bone metastases. The osseous metastases were investigated with 5-hydroxytryptophan, radio-labelled with 11C in the carboxyl group (5-HTC), and with 5-HTP in order to elucidate in vivo the presence of hydroxytryptophan decarboxylation. An increased uptake, measured as standard uptake value (SUV), in the metastatic lesions was observed using 5-HTP. The uptake varied between lesions. Using 5-HTC a corresponding uptake was observed. The time-activity rates were similar. The congruence in uptake patterns between 5-HTP and 5-HTC in the investigated lesions, demonstrates that decarboxylation of 5-hydroxytryptophan to serotonin is not a dominant factor in the uptake. It was concluded that 5-HTC could be used in vivo to investigate the chemical event of decarboxylation of 5-hydroxytryptophan and provide information about characteristics in metastatic lesions.
authors.affiliation: Department of Oncology, University Hospital, Uppsala, Sweden.
authors.forename: K M
authors.initials: KM
authors.lastname: Kälkner
authors.forename: S
authors.initials: S
authors.lastname: Nilsson
authors.forename: M
authors.initials: M
authors.lastname: Bergström
authors.forename: K J
authors.initials: KJ
authors.lastname: Lindner
authors.forename: G
authors.initials: G
authors.lastname: Westerberg
authors.forename: B
authors.initials: B
authors.lastname: Långström
authors.forename: J E
authors.initials: JE
authors.lastname: Westlin
mesh_terms: D006916:5-Hydroxytryptophan / Q000378:metabolism* / Q000493:pharmacokinetics; D000230:Adenocarcinoma / Q000378:metabolism* / Q000556:secondary; D000368:Aged; D003653:Decarboxylation; D006801:Humans; D008297:Male; D008875:Middle Aged; D015394:Molecular Structure; D009376:Neoplasms, Hormone-Dependent / Q000378:metabolism* / Q000556:secondary; D011471:Prostatic Neoplasms / Q000378:metabolism*; D014055:Tomography, Emission-Computed / Q000379:methods*
chemical_list: D006916:5-Hydroxytryptophan