Introduction: Cancer antigen 15-3 (CA 15-3) is the most widely used serum marker in diagnosing and monitoring breast cancer. The aim of this work was to analyze preoperative CA 15-3 serum levels in patients with ductal breast carcinoma in relation to 1) clinicopathological parameters, 2) hormone receptors, and 3) tissue-based tumor markers.
Methods: A group of 340 women with infiltrating ductal carcinoma of the breast who had undergone no prior treatment was studied. These women ranged in age between 27 and 83 years (mean age 61.5±9.9 years). Preoperative CA 15-3 serum levels were determined by an immunoradiometric method. Hormone receptors (estrogen, progesterone and androgen receptors), p53, bcl-2 and Ki67 were determined by different immunohistochemical methods. Epidermal growth factor receptor (EGFR) was analyzed in the cell membranes by radioligand assay whereas cathepsin D and pS2 were determined by immunoradiometric analysis. Tumor ploidy and S-phase fraction were studied by flow cytometry.
Results: CA 15-3 serum levels were higher in postmenopausal women (p=0.032), in patients with tumors exceeding 2 cm (p=0.003), lymph node involvement (p=0.026), distant metastases (M1) (p<0.0001), S-phase fraction <7% (p=0.015), EGFR <6 fmol/mg protein (p=0.025), and cathepsin D <50 pmol/mg protein (p=0.023).
Conclusions: Preoperative CA 15-3 serum levels were associated with cell proliferation determined by the S-phase fraction, the concentration of cathepsin D in the cytosol, and the EGFR concentration in the cell membrane.