Which markers are used to monitor breast cancer therapy?

• A. HER2/neu and ER/PR
• B. CA 15.3 and CA 27.29
• C. BRCA1 and BRCA2
• D. CA 19-9

Answer: (B)

Tumor markers used to monitor breast cancer therapy reflect changes in tumor burden over time, helping clinicians gauge how well treatment is working. The markers most commonly used for this purpose are CA 15-3 and CA 27.29. They are shed from breast cancer cells and rise with higher tumor activity, so tracking their levels across treatment can show whether the disease is shrinking, stabilizing, or progressing. It’s important to remember that these markers are not perfect: some patients with active disease may have normal levels, and elevations can occur with benign liver conditions, inflammation, pregnancy, or other cancers. Because of that, they are used in conjunction with imaging studies and clinical exams rather than as a sole measure.

Markers like HER2/neu and ER/PR status are not used to monitor how the disease responds over time; they guide treatment choices—HER2 status determines eligibility for HER2-targeted therapies, and ER/PR status informs endocrine therapy decisions. BRCA1 and BRCA2 are genetic risk markers indicating predisposition to breast and other cancers, not real-time indicators of how the current disease is responding to therapy. CA 19-9 is a marker more relevant to pancreatic and some gastrointestinal cancers, not typical for breast cancer monitoring.