TC-99(M)-IMMU4 IMAGING IN RECURRENT COLORECTAL-CANCER - EFFICACY AND IMPACT ON SURGICAL-MANAGEMENT

The aims of this study were to evaluate the efficacy of scintigraphy w ith the Tc-99(m)-labelled anti-carcinoembryonic antigen (CEA) monoclon al antibody Fab' fragment (IMMU4) in the diagnosis of recurrent colore ctal carcinoma and to investigate its usefulness in the intraoperative surgical management of patients undergoing re-operation because of a rising serum CEA. We evaluated 24 patients prospectively who had risin g serum CEA 6-19 months after initial surgery for colorectal carcinoma . Ten patients had lesions confirmed by computed tomography, ultrasoun d, magnetic resonance imaging, endoscopic examination Or barium enema. Fourteen patients had negative findings on one or more of the above s tudies, but were suspected of having occult disease from their rising serum CEA. All patients were scheduled for surgery for restaging durin g a 'second look' procedure. Planar and single photon emission tomogra phy (SPET) imaging was performed in all patients. All scintigraphic fi ndings were correlated with surgical and histopathological results. Th e overall sensitivity, specificity and accuracy were 81, 90 and 86% re spectively when analysed by lesion, and 95, 60 and 88% respectively wh en analysed by patient. Ten of 14 (71%) patients with occult disease w ere correctly diagnosed as having recurrent disease. The SPET images w ere shown to have superior detectability (80%) compared with the plana r images (35%). The surgeon judged the study to have had a neutral imp act in 75% of the patients, but to have been helpful in 25%. We conclu de that this antibody is potentially useful in detecting recurrent col orectal carcinoma in patients with rising serum CEA, especially when c onventional imaging is negative or equivocal. It can also be helpful i n altering planned surgery.