This test measures Cancer Antigen 15-3, a protein released by breast cancer cells into the bloodstream.
Diagnostic Value: Elevated CA 15-3 levels are often associated with advanced or metastatic breast cancer, particularly in hormone receptor–positive cases.
Clinical Significance: It is primarily used to monitor treatment effectiveness, recurrence, or progression rather than for initial diagnosis.
Symptom Correlation: Rising levels may coincide with new pain, swelling, or weight loss in patients with known breast malignancy.
Because it reflects changes in tumor activity over time, CA 15-3 testing is valuable in tracking breast cancer treatment and recurrence risk.