The Value of Immunoscintigraphy for the Operative Retreatment of Colorectal Cancer. Limitations of a New Diagnostic Method

In 42 patients with suspected recurrent colorectal cancer, results of conventional diagnostic methods were compared with those of immunoscintigraphy. In 69% of all cases, the intraoperative findings of a second-look operation served for validation, whereas in 31% close follow-up was used. Recurrent tumors were successfully localized in 83% of patients by conventional methods, whereas immunoscintigraphy was expressive in 57% of cases. Immunoscintigraphy was disappointing especially because of its low sensitivity (23%) and low predictive value (positive, 33%; negative, 37%) with regard to successful diagnosis of extrahepatic tumors compared with the results of conventional methods (77% sensitivity; positive, 94%; negative, 79%). The rate of false-positive results was relatively high with immunoscintigraphy (n = 12), 83% of which were related to extrahepatic recurrent tumors. The value of immunoscintigraphy using an immunococktail of 131-J-labeled F(ab')2 fragments of monoclonal antibodies against CEA, with Ca 19-9 as an additional diagnostic tool for early detection of recurrent colorectal cancer, must therefore be viewed critically.