CLINICAL-EVALUATION OF METASTASES OF MALIGNANT-MELANOMA IMAGING WITH TC-99(M)-GLUTATHIONE AND TC-99(M)-ANTI-MELANOMA ANTIBODY - A COMPARATIVE-STUDY

The aim of this investigation was to test for the scintigraphic detect ion of metastases of malignant melanoma with a new radiopharmaceutical , Tc-99(m)-glutathione (Tc-99(m)-GSH), in comparison with Tc-99(m)-ant i-melanoma antibody (Tc-99(m)-AMAb). Glutathione was labelled with Tc- 99(m) by a Sn2+ reduction method with an efficiency of > 99% as determ ined by instant thin layer chromatography (ITLC). Anti-melanoma antibo dy was obtained as a kit from SORIN (Italy) and labelled with (TcO4-)- Tc-99-O-m. Forty-three patients with a total of 55 biopsy-proven metas tatic melanoma foci, 1 ocular melanoma and 20 benign pathologic foci, also confirmed by ultrasound, computed tomography and magnetic resonan ce imaging, were included in the study after giving their informed con sent. Following the intravenous (i.v.) injection of 500 MBq Tc-99(m)-A MAb, scintigraphic images of the involved areas were obtained 6 h post -injection. Three days later, the same patients were given 500 MBq Tc- 99(m)-GSH i.v, and images were obtained 6 and 24 h post-injection. The images were classified as positive (focal abnormal accumulation) or n egative. Quantitative evaluation was also applied. Regions of interest were drawn over the involved areas and nearby soft tissues and the ta rget-to-nontarget (T/NT) ratios obtained with Tc-99(m)-AMAb (T/NT: 1.9 2 +/- 0.2) and Tc-99(m)-GSH (T/NT: 1.84 +/- 0.2) were compared (0.1 < P less than or equal to 0.3). The sensitivity (and specificity) of Tc- 99(m)-AMAb and Tc-99(m)-GSH in the detection of malignant melanoma met astases were 91% (95%) and 84% (90%), respectively. Compared with Tc-9 9(m)-AMAb, the advantages of Tc-99(m)-GSH are lower levels of blood ra dioactivity, lower costs and easy in-house preparation. In conclusion, our results show that Tc-99(m)-GSH is a potentially useful radiopharm aceutical for the detection of metastases of malignant melanoma.