Immune-scintigraphy of recurrent colorectal tumors with Tc-99m-marked monoclonal carcinoembryonic antigen antibodies

After surgery in 24 patients aged 39-80 years with colorectal tumors, immune-scintigraphic examinations with Tc-99m carcinoembryonic antigen (CEA) MAb were carried out. Prior to scintigraphy, the levels of CEA and Ca 19-9 tumor markers were determined. In the majority of cases there was firm clinical evidence of local recurrence or metastases. Twenty-two of the 24 cases were scintigraphically positive. Local recurrence and metastases of the liver were correctly identified in 12 and four cases, respectively. It was difficult to detect widespread metastases of the peritoneum or a growth at the helum of the lung. In three cases, metastases of lymph nodes were confirmed by both surgery and scintigraphy, although the computed tomographic (CT) examinations were negative. In 20 patients, CT and immune-scintigraphic findings correlated. Most positive scans were confirmed surgically and at biopsy. In two patients, none of the diagnostic procedures showed positive results, despite clinical grounds for suspecting a further spread of the disease. A false-positive immune-scintigram was observed in a histologically confirmed case of inflammation of the mucous membrane. In several cases Tc-99m enhancement was detected in almost all parts of the colon. This could be due to the antibody metabolism or to the deposit of free technetium in the bowel. There was no correlation between CEA serum levels and a positive immune-scan