The role of cancer antigen 15-3 and carcinoembryonic antigen in assessing treatment response in patients with metastatic breast cancer

Background: In breast cancer, the most widely used tumor markers are cancer antigen 15-3 (CA 15-3) and carcinoembryonic antigen (CEA). These markers are primarily used for surveillance purposes and monitoring of treatment responses in clinical practice. This study aims to examine the role of CA 15-3 and CEA in assessing treatment response in patients with metastatic breast cancer (MBC). Methods: This study was investigated 45 MBC patients who met the eligibility criteria. We evaluated the levels of CA 15-3 and CEA before chemotherapy, after 3 months, and after 6 months. The response to therapy was assessed by imaging. Results: There were statistically significant differences between changes in CA 15-3 and CEA after 6 months of chemotherapy and treatment response as assessed by imaging (p<0.001 and p=0.002, respectively). The CA 15-3 level of good responders at 6 months after chemotherapy decreased by 32.3% from the baseline level, while that of poor responders increased by 141.6% from the baseline level, which was statistically significant (p<0.001). The CEA level of good responders at 6 months after chemotherapy decreased by 0.03% from the baseline level, while that of poor responders increased by 182.38% from the baseline level, which was statistically significant (p=0.012). Conclusions: Our results showed a clear correlation between tumor markers and treatment response as assessed by radiological methods. The use of tumor markers for assessing treatment response has several advantages, including availability, cost savings, and no radiation exposure. Tumor markers can potentially reduce the need for frequent radiological assessments.