[Radioimmunoscintimetry for intraoperative lymph node diagnosis in colorectal cancer].

In a prospective study 32 patients with primary colorectal carcinomas were studied by means of radioimmunoscintigraphy with the anti-carcinoembryonic antigen monoclonal antibody BW 431/26 labelled with either 131I (group 1, n = 17) or 99Tc (group 2, n = 15). Scintigraphy of the resected specimen was used as a model for intraoperative radioimmunoscintimetry, and all positive lymph nodes were marked during the investigation. The results were compared with the data yielded by preoperative investigations (CT, MR, endosonography) and checked by histology and immunohistochemistry. The analysis (sensitivity, specificity) included: type of investigation, time interval from antigen application, type of radionuclide, size of lymph nodes investigated, and serum level of CEA. 131I-Scintigraphy of the resected specimen gave the best results in the detection of lymph node metastases (sensitivity 1, specificity 0.57) and was superior to all other diagnostic procedures. When the investigation was performed 6-8 days after administration of the antibody the specificity improved to 1. The best results (sensitivity 1, specificity 0.91) were achieved in small (< 1 cm) lymph node metastases. A good correlation between scintigraphic diagnosis and immunohistochemical CEA detection was confirmed. Serum levels of CEA had no influence on the scintigraphic results. We conclude that intraoperative radioimmunodetection of lymph node metastases may improve the radicality in the resection of colorectal tumors. The best results are achieved with 131I-labelling and with application of the antibody 6-8 days before the operation.