Radioimmunolocalization and selection for surgery in recurrent colorectal cancer.

The value of radioimmunolocalization (RIL) of cancer depends on its performance in situations where the result determines the choice of management. A rise in serum carcinoembryonic antigen (CEA) values after apparently curative resection of colorectal cancer implies localized, resectable recurrence in some patients and widespread unresectable tumour in others. This study investigated the ability of RIL with radiolabelled antibody to CEA and a novel numerical method for analysis of results to determine the extent of disease in 31 patients with raised serum CEA but no physical signs of recurrence. Surgical exploration or conventional radiology later confirmed the presence of tumour in 94 per cent of sites which were positive by RIL. Negative RIL predicted the absence of disease in 53 per cent of patients. The investigation could discriminate between localized and disseminated disease and often performed better than conventional radiology. RIL appears useful in selection of patients for second look laparotomy.