Colon Carcinoma Immunoscintigraphy by Monoclonal Anti-CEA Antibody Labeled with Gallium-67-Aminooxyacetyldeferroxamine

Previous experimental results in nude mice showing that radiolabeling the monoclonal antibody anti-CEA 35 with 67Ga-aminooxyacetyldeferroxamine could give better tumor localization than radioiodination prompted us to initiate the present clinical study. The 67Ga-labeled antibody anti-CEA 35 (185 MBq, 0.7-1.7 mg) was injected preoperatively into 14 patients for colorectal carcinoma imaging. The same antibody labeled with 125I (3.7 MBq, 0.25 mg) was injected simultaneously to compare the 67Ga and 125I dose recoveries in surgical specimens. Twelve of 14 primary tumors gave a positive 67Ga scintigraph. The mean %ID/g recovered in all tumors 3-9 days after injection was significantly higher for 67Ga (0.019%) than for 125I (0.005%) (p < 0.001, paired t test). The tumor-to-normal tissue ratios were generally higher for 67Ga, with the exception of liver. We conclude that 67Ga-aminooxyacetyldeferroxamine improved immunoscintigraphy outside the liver, particularly in the pelvic region. We also show that deferroxamine infusion accelerates the excretion of 67Ga in eight patients and propose that this could lead to further improvement of immunoscintigraphy.