Role of tumor-associated antigen expression in radioimmunoguided surgery for colorectal and breast cancer.

One hundred thirty-six patients with colorectal and breast cancer were enrolled in a retrospective study using radioimmunoguided surgery (RIGS) with Iodine-125 (I125) radiolabeled B72.3 (Group A, 73 patients) and F023C5 (Group B, 63 patients) monoclonal antibodies (MAbs). The correlation between intraoperative tumor-to-normal tissue (T/NT) gamma-detecting probe (GDP) counts ratio and the expression of tumor-associated glycoprotein (TAG)-72 (GroupA patients) and carcinoembryonic antigen (CEA; Group B patients) tumor-associated antigens (TAA) expression of 209 resected or biopsy tumor specimens was assessed. Ex vivo radioimmunolocalization index (R.I.) was carried out on the same specimens as a control of intraoperative GDP ratio values. RIGS positive definition of tumor occurred in 80/113 (70.8%) tumor sites of Group A patients and in 84/96 (87.5%) tumor sites of Group B patients. Mean percent B72.3 TAA expression of 113 tumor sites of Group A patients was 62.74 +/- 28.79% vs. 73.00 +/- 26.28% of 96 tumor sites of Group B patients (P < 0.05). The higher incidence of positive RIGS results was observed in tumor sites with the higher expression of the relative TAA. A statistically significant correlation between RIGS ratios and B72.3 and CEA expression was observed in the 113 tumor sites of Group A (P < 0.05) and in the 96 tumor sites of Group B (P < 0.01), respectively. The role of a preoperative evaluation of TAA expression in patients undergoing RIGS is discussed. Its assessment, whenever possible, may help to select those patients who will benefit more from this immunodiagnostic technique.