111In-CYT-103 scanning in recurrent colorectal cancer--does it affect standard management?

In a blinded fashion, radiolabeled B72.3 was investigated in operative cases of recurrent colorectal cancer to determine if diagnostic accuracy would be improved to ultimately maximize curability and minimize interventional morbidities.

Study patients underwent conventional evaluation including history, physical examination, abdominal/pelvic computed tomographic scan (CT), colon examination, and carcinoembryonic antigen (CEA) determination, with select magnetic resonance imaging and ultrasonographic imaging as indicated. Murine monoclonal antibody B72.3 was labeled with indium-111 (111In-CYT-103 provided by Cytogen) and scans obtained at 48 hours and, selectively, at 72 and 96 hours. Unlike previous studies, the operating surgeon was blinded to 111In-CYT-103 abdominal scan results until surgical exploration was complete.

Of 15 study patients (10 male; 5 female), average age was 57 years, and average CEA was 10 ng/ml (with eight elevated CEA levels). A single patient did not undergo surgery because of presence of pulmonary metastases identified on CT scan but not identified on a 111In-CYT-103 scan. Laparotomies included resection and intraoperative radiation (10), resection alone (1), and biopsy only (3). CT and 111In-CYT-103 scans were compared with operative findings. CT scans had an accuracy and positive predictive value of 47 and 100 percent, respectively, whereas those of 111In-CYT-103 scan were 60 and 82 percent, respectively. Contribution of the scan to diagnosis and management was graded by the surgeon as no effect (67 percent), beneficial effect (13 percent), or negative effect (20 percent).

111In-CYT-103 was more accurate compared with CT scan, but when value of the scan was examined with respect to its potential contribution to patient management, it was beneficial in only 13 percent of patients. Further refinements may enhance the value of antibody imaging techniques.