Published in Cancer Detection and Prevention 2000; 24(Supplement 1).

3-O-6-methyl [18f]fluor-l-dopa - a new radiolabeled amino acid for tumor targeting with positron emission tomography

W Franke MD 1, H Ahlheit MD 2, B Beuthien-Baumann MD 3, J Bredow MD 4, P Brust PhD 5, F Fuechtner PhD 6

1,2,3,4 University of Technology Dresden University Hospital, Dresden, Germany, 5,6 PET Centre Rossendorf, Dresden, Germany,

AIMS: Positron emission tomography (PET) plays an important role in targeting of some kinds of tumors. However, development of new radiopharmaceuticals is inevitable to extend the method to further tumor species. METHODS : 18F labelled amino acid "3-O-6-methyl- fluoro L-DOPA"(OMFD) was sythesized from the new precursor"N-formyl-3-o-methyl-4-O-Boc-6-trimethylstannyl-L-DOPA-ethyl-ester". Biologic behavior was tested in HAT 29 RBE-4-cell cultures and tumor bearing nude mice (SC-Ca). Nine follow - up - assessments took place in 8 patient with recurrent glioblastoma (4) and low grade astrocytomas (4) as well as 1 brain stem tumors and 1metastasis . MRT and CT were inconclusive in each of these cases. The aim of the PET studies was to detect localization and extent of recurrence for planning of stereotactic radiotherapy. RESULTS: After 50 minutes sythesis time a radiochemical yield of 20-25 % was reached. A high tracer uptake in tumor cells probably via L-amino-transporter was seen. There was no evidence for incorporation into proteins. A high tumor / blood-ratio(9.5 ±0.8) accompanied by intensive intratumoral uptake (12.4±1.8% ID/ g) was found in animal experiments with tumor bearing nude mice. Raised radioactivity uptake was detected in all patients 60 min pi. in the suspected tumor region (lesion/nonlesion 2.2±0.5). Suspected tumor lesions were presented clearly at the PET scans .CONCLUSIONS: These preliminary studies suggest that OMFD is a valuable tracer for tumor targeting in vivo esp. in recurrences of brain tumors.

KEY WORDS: recurrent glioblastoma, low grade astrocytoma, intensive intratumoral uptake, L-amino-transporter, tumor bearing nude mice.

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Paper presented at the International Symposium on Impact of Biotechnology on Cancer Diagnostic & Prognostic Indicators; Geneva, Switzerland; October 28 - 31, 2000; in the section on differentiation therapy.