PREPARATION OF YTTRIUM-90-LABELED HUMAN MACROAGGREGATED ALBUMIN FOR REGIONAL RADIOTHERAPY

Human macroaggregated albumin (MAA), which is currently labeled with t echnetium-99m (Tc-99m) and Tc-99m MAA, is used clinically as a pulmona ry perfusion agent and was directly labeled with yttrium-90 (Y-90) ace tate. This study evaluated whether Y-90-MAA could be a potential radio therapeutic agent for regional radiotherapy against malignant tumors. MAA suspended in 0.1 M sodium acetate buffer, pH 5.8, was incubated wi th Y-90 acetate and purified in order to get rid of unstable binding o f Y-90 by electrophoresis. The radiochemical purity of Y-90-MAA in nor mal human serum was estimated by an agarose electrophoresis method and was more than 94% over 168 h in vitro. Following the intratumoral adm inistration of Y-90-MAA, the time course of tumor radioactivity and th e biodistribution in nude mice bearing human neuroblastoma were invest igated up to 168 h. More than 93% of the radioactivity of the injected dose was found on the subcutaneous tumor over 168 h. The bone radioac tivity was shown as 0.06 +/- 0.03% injection dose/gram tissue (% ID/g) (n = 5) at 24 h, 0.73 +/- 0.20% ID/g at. 72 h, 0.92 +/- 0.16% ID/g at 120 h, and 2.51 +/- 0.59% ID/g at 168 h. A slight increase in radioac tivity was noted in the liver, kidneys, and spleen over the 168 h peri od. In conclusion, Y-90-MAA may be a potential agent for regional radi otherapy (brachytherapy) because of the sufficient persistence in the tumor following an intratumoral administration. (C) 1997 Elsevier Scie nce Inc.