Study of secretory component in patients with metastatic breast cancer.

A radioimmunoassay was developed for secretory component, a glandular epithelial cell product secreted as an accessory protein with dimeric immunoglobulins A and M. Forty-four normal women between the ages of 40 and 70 had plasma concentrations of secretory component of 7.195 microgram/ml +/- 3.590 (+/-2 SD). Of the patients with metastic breast cancer of epithelial origin, 34 (91.9%) had plasma concentrations greater than 8.990 microgram/ml; 29 (78.1%) had plasma concentrations greater than 10.785 microgram/ml; 10 (27%) had concentrations greater than 15.000 microgram/ml; and 3 (8.1%) had concentrations greater than 22.710 microgram/ml. Serial plasma concentrations (averaging 3.48 per patient) of 35 (94.6%) of these patients reflected the clinical course of the disease. All patients had some combination of surgery, radiation therapy, and chemotherapy. No direct correlation was noted between the type of therapy and concentration of secretory component. However, plasma secretory component served as a marker in the systemic circulation of a change in the status of the metastatic breast cancer. The impact of this research may lie in its incorporation into clinical management.