Antigen-directed cancer surgery for primary colorectal cancer: 15-year survival analysis

Tumor-associated glycoprotein-72 (TAG-72) is a mucin-like high-molecular-weight glycosylated protein complex overexpressed by many adenocarcinomas. Antigen-directed cancer surgery using radiolabeled anti-TAG-72 murine monoclonal antibodies (muMAbs) has been previously investigated for colorectal cancer. Survival analysis of primary colorectal cancer patients with a minimum of 15-year follow-up after antigen-directed cancer surgery was performed to assess the impact of complete surgical resection of all detectable radiolabeled anti-TAG-72 muMAb.

Survival analysis was performed on 92 patients (study group) with primary colorectal cancer (July 1990 to August 1995) treated with antigen-directed cancer surgery using (125)I-labeled anti-TAG-72 muMAb. The study group was subdivided into those with no detectable TAG-72 antigen-bearing tissues (TAG-72 negative, N=33) and those with persistent detectable TAG-72 antigen-bearing tissues (TAG-72 positive, N=59) at completion of surgery. Comparisons were made with a control group (546 patients) from the same time period.

Study group and control group were demographically similar, as were TAG-72-negative subgroup and TAG-72-positive subgroup. TAG-72-negative subgroup had significantly improved median survival (8.8 versus 2.5 years; P=0.005) and time-dependent survival (45.4% versus 22.0% at 10 years; P=0.002 and 39.4% versus 20.3% at 15 years; P=0.003) compared with TAG-72-positive subgroup. TAG-72 positivity was as an independent predictor of long-term mortality risk, when controlled for pathologic stage of disease.

Absence of detectable TAG-72 antigen within the surgical field at completion of antigen-directed cancer surgery for primary colorectal cancer is of significant prognostic value, conferring a long-term survival advantage to those in whom complete surgical removal of all tissues with detectable radiolabeled anti-TAG-72 muMAb was accomplished.