Background: CA15.3 (also known as MUCI) is the most widely used marker in breast cancer. The aim of the present work was the evaluation of the prognostic value of preoperative serum CA15.3 levels in patients with primary breast cancer.
Patients and methods: This study included 818 women with a histologically verified diagnosis of invasive breast cancer. The serum values of CA15.3 were investigated at the time of primary diagnosis by means of an immunoradiometric assay based on the "sandwich" principle. The median follow-up period of patients free of recurrence was 38 months.
Results: Pre-operative CA15.3 serum levels ranged from 6 to 452 U/ml. Elevated CA15.3 levels (>30 U/ml) were found in 15.2% of patients. Statistical analysis showed that pre-operative CA15.3 serum levels were significantly higher in patients with large size tumors (T3 or T4) (p = 0.0001), as well as in those with node-positive tumors (p = 0.0001). In the univariate analysis, high CA15.3 levels were significantly associated with a lower probability of both relapse-free and overall survival in the overall group of patients (p = 0.0001 and p = 0.004, respectively) and in the subgroup with node-positive breast cancer (p = 0.001 and p = 0.03, respectively). In addition, multivariate analysis demonstrated that pre-operative levels of the antigen were significantly and independently associated with relapse-free survival in the overall group of patients, as well as in the subgroup of patients with node-positive breast cancer (p = 0.02 and p = 0.01, respectively).
Conclusion: These results show that high pre-operative CA15.3 levels correlate with large size tumors and the presence of lymph node metastases and suggest that this antigen could be used as an additional prognostic marker.