Biomarkers to guide the treatment of metastatic breast cancer

This analysis provides recommendations on the correct use of biomarkers to guide decisions on systemic therapy for metastatic breast cancer. The article concluded that it is important that the medical community continue to carry out high-quality biomarker research for women with advanced breast cancer.

To help doctors provide the best care for their patients, the American Society of Clinical Oncology has developed biomarker guidelines to help guide decisions on systemic therapy for metastatic breast cancer. Metastatic breast cancer is cancer that has spread beyond the breast to other parts of the body. This may be treated with systemic therapy (such as chemotherapy) that travel through the blood to affect cells all around the body. Doctors can use biomarkers to decide if systemic therapy is the best treatment option for the patient.

Biomarkers are naturally occurring body substances that are associated with a disease and are often used for predicting disease progression. Cancer biomarkers include the estrogen receptor (ER) and the progesterone receptor (PR). ER or PR positive cancer depends on estrogen or progesterone to grow. HER2 status is also a cancer biomarker. HER2 positive breast cancer means that the cancer is dependent on the human epidermal growth factor receptor 2 for growth.  Cancer antigen 15-3 (CA 15-3), cancer antigen 27-29 (CA 27-29), and carcinoembryonic antigen (CEA) are biomarkers that may be found in the blood of people with breast cancer. 

The current analysis provided recommendations on the appropriate use of biomarkers to guide decisions on systemic therapy for metastatic breast cancer. 17 studies were included in the analysis.

A biopsy (an examination of tissue removed from the body) should be performed in areas where the tumor has spread. The biopsy will allow for testing of the ER, PR, and HER2 biomarkers. The ER, PR, and HER2 status of a tumor may change once it has spread. In this case it is recommended that the ER, PR, and HER2 status of the areas where the tumor has spread should be used to direct therapy. CEA, CA 15-3, and CA 27-29 are biomarkers that may be used to add to information that the doctor already has. However, these biomarkers should not be used alone to guide treatment or for monitoring how well treatment is working.

In patients already receiving systemic therapy for metastatic breast cancer, decisions on changing to a new drug or discontinuing treatment should be based on factors other than biomarkers, such as how much and where the tumor has grown and the patients overall health, treatment preferences and goals. 

This analysis concluded that it is important that the medical community continue to carry out high-quality biomarker research for women with advanced breast cancer.

A limitation of this review is that in many cases the tests for the biomarkers have not been validated for use in the clinic. Validation studies for these tests are currently ongoing and experts await the publication of the results.