Evaluation of the BT-1 serum assay for breast cancer.

The BT-1 assay which identifies a novel breast tumor associated serum analyte was performed for 143 patients previously diagnosed with breast cancer. Mucin tumor markers CA15-3/CA27-29 values were available for 50 patients and there was very minor overlap between patients positive by both tests. Patients' follow-up clinical status at sample draw was compared to BT-1 assay results. 27% of patients originally diagnosed as Stage II and 20% patients originally diagnosed as Stage III who were evaluated 'no disease' had positive BT-1 values. 8% patients diagnosed as Stage II had negative BT-1 results in samples drawn within 90 days of chemotherapy initiation, whereas 23% of patients diagnosed as Stage III cancer were BT-1 test positive within 90 days of chemotherapy initiation. 50% of patients tested before initial breast cancer surgery had positive BT-1 values, suggesting that the BT-1 assay may be useful in identification women with more advanced disease at diagnosis.