97Ru-transferrin uptake in tumor and abscess.

The uptake of 97Ru-transferrin (Ru-TF) in tumor and abscess bearing animals was compared with 67Ga-citrate (Ga), 123I-transferrin (I-TF), and several other plasma proteins. Maximal concentration in tumor of Ru-TF in mice was three times higher than 67Ga-citrate (16.80 +/- 4.20 vs 5.08 +/- 0.58% D/g) although it occurred later (24 h compared with 67Ga which reached its maximum 2 h after injection). Whole body autoradiography (WBARG) with 103Ru-transferrin (103Ru-TF) in tumor and abscess bearing rats demonstrated details of the distribution within these lesions. Turpentine-induced abscesses in the rabbits could be visualized with the gamma camera as early as 30 min post-injection of Ru-TF. It seems, therefore, that Ru-TF can be used for tumor and abscess localization. The results indicate that Ru-TF may have some advantages over 67Ga-citrate because of the higher concentration in the lesions. 123I-transferrin reached a concentration in tumor similar to 67Ga (6.89 +/- 1.67 vs 5.08 +/- 0.58% D/g) but had a very low tumor to blood ratio (0.64). The three compounds investigated (Ru-TF, I-TF and ionic Ga, which binds instantaneously to TF in vivo) have a common ligand, transferrin. It appears, therefore, that tumor affinity is a property of the radionuclide-ligand complex rather than of the radionuclide itself.