99mTc-Cysteine-Glucosamine (99mTc-CG) in the evaluation of patients with malignant tumors. Histopathological correlation

18F fluorodeoxyglucose with PET(18FDG-PET) imaging is used to image tumors. Due to the high cost and low availability, PET is not accessible to many patients. Labelled 99mTc agents to be used with SPECT could be an alternative to 18FDG-PET. Glucosamine (G), a six-carbon amino sugar, enters the cells by a glucose transporter system and by phosphate and glycolytic pathways forms glucosamine-6-phosphate. Reacting G with cysteine (C) labeled with 99mTc (99mTcCG) could be used to show with SPECT hypermetabolic lesions similar to 18FDG-PET imaging. The aim of this study was to evaluate the imaging with 99mTc-CG in detecting tumors and correlate them with pathology. Material and Methods: Labelling of 99mTc-CG was done by adding (C), (G), N-hydroxysuccinimide, carbodiimide, and stannous chloride to the 99mTc. Patients: 35 patients (23 F, 12 M, range age 7-79 years, mean 52 ) with histopathology diagnosis were referred for scintigraphy with 99mTc-CG. Imaging: Patients fasted for 12 hr, and 1-4 hours after the i.v. injection of 920-1088 MBq of 99mTc-CG, underwent 1) whole body scan, 2) SPECT images (reconstructed with OSEM algorithm) on the field of view of the lesion. To eliminate the intravascular and interstitial activity of the 99mTcC-G imaging, patients were given 737 MBq of 99mTc human serum albumin(99mTc-HSA) and other SPECT was done. We normalized both SPECT images and subsequently the 99mTc-HSA image was subtracted from the 99mTc-CG image. All images were visually analysed. Results: 32 lesions were malignant (breast (5), colon (8), lung (9), Hodgkin's disease(6), thyroid(1), bladder (1), melanoma (1), ependimoma (1), and 3 were benign (brain radiation necrosis, breast inflammations and inespecific granuloma). 99mTc C-G show abnormal focal uptake in all malignant lesions (sensitivity=100%) as well as in two benign lesion (false positive). Accuracy of 99mTcC-G in patients with malign tumors was 94%. SPECT images defined the tumor uptake better than planar imaging. Image subtraction (99mTc-CG minus 99mTc-HAS) highlighted the 99mTcC-G abnormal uptake by eliminating the non-tumoral uptake.Conclusion: Our preliminary study showed that 99mTc-CG is a useful tool for metabolic imaging with SPECT, and might be a good alternative when 18FDG-PET is not available. Image subtraction is helpful in highlighting tumors uptake (au)