Radioimmunoguided surgery for recurrent colorectal cancer manifested by isolated CEA elevation

Carcinoembryonic antigen (CEA) is a sensitive marker for detecting recurrent colorectal carcinoma. An asymptomatic rise of CEA can precede by several months the detection of recurrent cancer by standard imaging modalities. Yet, surgeons are hesitant to operate solely on the basis of an observed increase in CEA. We investigated the ability of radioimmunoguided surgery to enhance the surgeon's capability of detecting intraabdominal disease in these patients.

Nineteen patients who underwent radioimmunoguided surgery for suspected tumor recurrence based solely on elevated CEA were included in the study. They underwent colonoscopy and CT of the abdomen and chest, all of which were negative. They then underwent scintigraphy scan with an anti-CEA monoclonal antibody (MoAb) labeled with (99m)Tc or Indium I-111. All patients were injected with the CC49 MoAb (an anti-TAG-72 tumor-associated glycoprotein) labeled with (125)I three weeks before surgery. During surgery, traditional exploration was followed by survey with a gamma-detecting probe.

Traditional surgical exploration identified 26 recurrent tumors: 7 hepatic, 8 pelvic, 6 retroperitoneal, 3 colonic, 1 splenic, and 1 anastomotic. Radioimmunoguided surgical exploration confirmed all recurrent tumors and identified additional tumor sites in seven patients that resulted in changing the surgical plan. CEA scans correlated with intraabdominal findings in seven patients. Abdominal pathology did not correlate completely with the scans in three patients, and CEA scan results were undetermined in two patients.

Patients with elevated CEA and no other findings should be operated upon without delay, and radioimmunoguided surgery should be used to enhance the surgeon's knowledge of the extent of disease.