Use of indium-111-labeled OC-125 monoclonal antibody in the detection of ovarian cancer

Abstract

This is a preliminary study to evaluate the utility of using the monoclonal antibody (CO-125) labeled with indium-111 to image recurrences of ovarian cancer. This technique has been investigated in 23 patients with ovarian cancer and the results have been compared with blood OC-125 levels, CT scans, and findings at second-look surgery. Following infusion of 1 mg of F(ab′) 2 fragments (1–2 mCi 111In), quantitative SPECT and planar imaging was obtained daily for 72 hr along with analysis of serum. The nuclear medicine scans of the tumor site recurrences were technically excellent. When compared to second-look laparotomy, there were 2 true negatives, 2 false positives, 14 true positives, and 2 false negatives by nuclear imaging. CT scans correlated less well with surgery, but serum OC-125 levels correlate more closely with nuclear scans and second-look surgery. Those with multiple small metastatic implants showed a pattern of diffuse uptake which increased with time, whereas those with nodal or larger recurrences showed a more focal uptake. The combination of favorable biodistribution and positive images, especially in patients with normal antigen levels and negative CT scans, suggests a role for OC-125 monoclonal antibody imaging in their clinical management. However, further investigation is needed to determine whether nuclear scans can replace second-look surgery. If it can show that enough 111In-labeled antibody accumulates in the tumor site to justify radioimmunotherapy, then 90Y (a pure beta emitter) could be exchanged for 111In. This is potentially a method of radioimmunotherapy for recurrent ovarian carcinoma.