Biomarkers for breast cancer diagnosis or screening

In America, breast cancer is the most common malignancy in females and the second leading cause of cancer deaths in women. The American Cancer Society estimates that there will be 271,270 new cases of breast cancer in 2019, 99% of which will be diagnosed in women.

It is a disease caused by a combination of genetic and environmental factors and not all patients have the same clinical picture. Early detection of breast cancer is of considerable clinical importance. In recent years, the serum concentration of tumor markers has been used to detect tumor activity.

A tumor marker is a substance present in or produced by cancer cells or other cells of the body in response to cancer or certain benign conditions that provides a minimally invasive cost-effective source of data valuable for monitoring disease course, determining prognosis, and helping in selecting an appropriate treatment.  A decrease in the level of a tumor marker may indicate that the cancer is responding to treatment. If there is no change or the tumor marker increases, this may indicate that the treatment is not working or that cancer has returned.

The American Society of Clinical Oncology (ASCO) has published its recommendations for use of tumor markers for breast cancer. The tumor markers that showed evidence of clinical utility include Carcinoembryonic antigen (CEA) and Cancer Antigen (CA) 15-3

Carcinoembryonic antigen

Also known as CEACAM. The heterogenous CEACAM (CEA-related cell adhesion molecule) family belongs to the immunoglobulin superfamily and comprises 12 genes in humans. The CEACAM proteins can interact homophilically and heterophilically with each other, suggesting that CEA might act as an adhesion molecule. The functions attributed to CEA family members are diverse and include modulation of tumor growth and elevated CEA is associated with metastatic disease.

Cancer antigen (CA)

Is a carbohydrate containing protein antigen called mucin (MUC) and according to their molecular and genetic characteristics CA 15-3 belongs to the MUC1 family. Overexpressing of the MUC1 gene in malignant breast tumor allowing used as tumor maker of breast cancer and is useful in determining the prognosis of breast cancer and to monitor the efficacy of therapy.

However, there are some limits to the use of tumor markers because there are non-cancerous conditions that can elevate the concentration of tumor markers and these may be considered when interpreting the test result.