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 Ga-67 aminooxyacetyldeferroxamine could give better tumor localization than radioiodination prompted us to initiate the present clinical study. The Ga-67-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 I-125 (3.7 MBq, 0.25 mg) was injected simultaneously to compare the Ga-67 and I-125 dose recoveries in surgical specimens. Twelve of 14 primary tumors gave a positive Ga-67 scintigraph. The mean %ID/g recovered in all tumors 3-9 days after injection was significantly higher for 67-Ga (0.019%) than for I-125 (0.005%) (p < 0.001, paired t test). The tumor-to-normal tissue ratios were generally higher for Ga-67, 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 Ga-67 in eight patients and propose that this could lead to further improvement of immunoscintigraphy.