Detection of pelvic recurrence of colorectal carcinoma: prospective, blinded comparison of Tc-99m-IMMU-4 monoclonal antibody scanning and CT.

Abstract

To prospectively compare the accuracy of imaging with technetium-99m-labeled Fab' fragment of the anti-carcinoembryonic antigen antibody (CEA) IMMU-4 with that of computed tomography (CT) for the detection of pelvic recurrence of colorectal carcinoma. In 61 patients, blinded interpretations of both modalities were correlated with surgical-pathologic (n = 23) or clinical and CT follow-up findings (n = 38). Sensitivity and specificity with antibody scanning alone and combined with CT (79% and 84% vs 83% and 81%, respectively) were not significantly different from those values for CT alone (66% and 97%, respectively). Sensitivity of antibody scanning was greater for recurrences larger than 2 cm (94% vs 55% [P = .02]), serum CEA more than 2.5 ng/mL (91% vs 40% [P = .03]), and combined planar and single photon emission CT antibody scanning compared with planar alone (79% vs 48% [P = .03]), without a significant decrease in specificity. Antibody scanning does not improve on findings at CT alone for recurrent colorectal carcinoma but can help differentiate recurrent tumor from fibrosis.