Purpose: Monoclonal antibody (moAB) TKH-2 directed to the tumor-associated O-linked sialyl 2-6-alpha-N-acetylgalactosaminyl (sialyl Tn; STN) epitope was generated by immunization with ovine submaxillary mucin (Kjeldsen et al, Cancer Res 48:2214-2220, 1988). We investigated whether circulating serum levels of STN antigen might influence the prognosis of patients with ovarian cancer.
Patients and methods: Serum samples were obtained from 126 healthy nonpregnant women, 157 patients with benign gynecologic disease, and 89 patients with histologically proven epithelial ovarian cancer. Circulating serum STN-antigen concentrations (U/mL) were determined by a competitive radioimmunoassay kit (Otsuka Assay Laboratories, Tokushima, Japan) in a one-step procedure.
Results: Serum antigen levels were elevated in 48.3% of the patients. The levels of STN antigen were significantly higher in the sera of patients with cancer when compared with levels in benign and healthy controls (P less than .05). The 5-year survival rate for patients with STN-negative (serum STN levels less than 50.0 U/mL) versus STN-positive (greater than or equal to 50 U/mL) tumors was 76.9% versus 10.8%, respectively (P less than .05). The progression-free interval (PFI) at 5 years was 51.9% versus 5.4%, respectively (P less than .05). The overall survival probability and PFI were worse in patients with STN-positive sera. Multivariate regression analysis revealed that stage, residual tumor size, positive STN, performance status, and histologic grade were the five important variables for predicting overall survival.
Conclusion: We conclude that a positive STN-antigen level in sera is an independent predictor of poor prognosis in ovarian cancer.