UICC World Cancer Congress 2006

Objective:Methionine is an essential amino acid that is uniquely metabolized to the key biochemical intermediate, S-adenosylmethionine. Tumor-associated methionine dependence has been attributed to increased demands of cellular methylation pathways rather than of the protein machinery. The cost effectiveness & nonavailability of Cyclotron in underdeveloped & developing countries is a basic problem. Demonstration of differentiating glioma with non-tumoral lesions and the recurrence of tumor from radiation induced necrosis in human tumors without surgical intervention. Therefore studies were undertaken after labeling Methionine with reactor produced Technetium-99m for its possible use in brain tumor imaging.

Methods:The methionine, a nonpolar amino acid was labeled with Technetium-99m after modifying certain steps as reported by Tubis et al, and also by transchelating methods. We used both Chelation & transchelation methods for radiolabelling. The tumor uptake was correlated with tumor using methionine retention index using two different methods of radiolabelling.The uptake was calculated using Region of interest programme.ITLC method for chromatography & proton NMR were applied to assess the Quality & radiolabelling of the 99mTc-methionine.

Results:: In our studies the labeling efficiencies were in order of 99 % & 97 % with chelating & transchelating mehods.NMR studies indicated the binding of Tc-99m with one of the isomers of methionine where shifting of proton peak of tagged isomer was recorded.The higher accumulation of Tc-99m methionine was seen in tumerogenic lesion of brain and was capable of differentiating recurrence from radiation necrosis.The retention index was higher on tumor bearing sites.