Association of Cancer Antigen 15-3 Levels and Metastasis in Clinically Diagnosed Early Breast Cancer Patients

Abstract

Introduction: Breast cancer is the most common malignancy among women worldwide and remains a major cause of cancer-related mortality. Early identification of metastatic disease is essential for prognosis and treatment planning. Cancer Antigen 15-3 (CA 15-3), a serum tumour marker derived from the MUC1 glycoprotein, has been widely studied for its role in monitoring breast cancer progression and metastasis. The present study was conducted to evaluate the association between serum CA 15-3 levels and metastasis in patients with clinically detected early breast cancer. Materials and Methods: A prospective observational study was conducted in the Department of General Surgery, Sri Guru Ram Das Institute of Medical Sciences and Research, Vallah, Amritsar, from July 2024 to December 2025. A total of 80 patients with biopsy-proven early breast carcinoma were included. Serum CA 15-3 levels were estimated using an automated electrochemiluminescence immunoassay system. A cut-off value of >30 U/mL was considered elevated. Patients with elevated CA 15-3 levels underwent radiological investigations for detection of metastatic disease. Statistical analysis was performed using SPSS version 26, and p-value < 0.05 was considered statistically significant. Results: The mean age of the study population was 57.29 ± 12.68 years. Elevated CA 15-3 levels were observed in 27 patients (33.75%), while 53 patients (66.25%) had normal levels. Distant metastasis was present in 24 patients (30.0%), with liver metastasis being the most common site. Significant associations were observed between elevated CA 15-3 levels and clinical nodal status (p = 0.0002), histological grade (p = 0.038), lymph node involvement (p = 0.001), and metastatic status (p < 0.001). All patients with metastatic disease demonstrated elevated CA 15-3 levels, whereas none of the patients with normal CA 15-3 levels had metastasis. Conclusion: Serum CA 15-3 levels showed a strong association with metastatic disease and other adverse prognostic factors in early breast cancer patients. Elevated CA 15-3 may serve as a useful non-invasive biomarker for identifying patients at increased risk of metastasis and may support prognostication and surveillance.