I-fibrinogen as an oncophilic radiodiagnostic agent: distribution kinetics in tumour-bearing mice.

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 substantial tumour-related compartment in the abnormal mice. The tumour concentration steadily increased for 4 h after injection, at which time it reached a peak concentration 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 123I 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 123I for scintigraphic imaging, could lead to a very useful radiodiagnostic procedure for cancer.