*I-FIBRINOGEN AS AN ONCOPHILIC RADIODIAGNOSTIC AGENT: DISTRIBUTION KINETICS IN TUMOUR-BEARING MICE

Summary.-Fibrinogen radioiodinated by the iodine monochloride method was tested as a tumour radiodiagnostic agent in mice. The *I-fibrinogen cleared from the blood of tumour-bearing mice more rapidly than from that of normal mice, but it cleared from the whole body more slowly, suggesting it accumulated in a sub-stantial tumour-related compartment in the abnormal mice. The tumour concentra-tion steadily increased for 4 h after injection, at which time it reached a peak concen-tration of 11.4 % of the injected dose/g. This concentration was higher than the peak concentration for Ga-citrate (not reached until 24 h) or any other oncophilic radiopharmaceutical tested in this tumour model. The early accumulation is consistent with the use of 1231 as a tracer label for fibrinogen. A combination of the large tumour concentration of *I-fibrinogen, an increased catabolic rate induced by chemical modification, and the exceptional nuclear properties of 1231 for scintigraphic imaging, could lead to a very useful radiodiagnostic procedure for cancer. INDEPENDENT observations by bot