Biomarkers to Guide Treatment for Early-Stage Breast Cancer

February 8, 2016

To help doctors provide their patients with the highest quality care, the American Society of Clinical Oncology (ASCO) developed a new guideline on how to use biomarkers to guide the treatment of early-stage breast cancer. This guide for patients is based on ASCO’s most recent recommendations.

Understanding biomarkers

A biomarker is a substance that is found in the blood, urine, or tumor of a person with cancer. It is made by the tumor or by the body in response to the cancer. A biomarker may also be called a tumor marker, and can be found in or on the tumor itself. Biomarkers help doctors learn more about each person’s cancer and recommend the best treatment options for each patient.

Biomarkers for breast cancer

The biomarkers listed below are most commonly used for breast cancer. When you are diagnosed with breast cancer, your doctor will recommend testing the cancerous tissue for these biomarkers. Testing is important because knowing whether a tumor marker is there or not can strongly affect your treatment choices.

  • Estrogen receptor (ER) and progesterone receptor (PR). Cancer cells sometimes use hormones in the body to grow, so it is important to know if this is true for each patient. Breast cancer cells that have ER and/or PR depend on estrogen and/or progesterone to grow. Testing for ER and PR can find out whether treating a cancer with hormonal therapy may work. Hormonal therapy may also be called endocrine therapy. Examples of hormonal therapy include the following:

    • Aromatase inhibitors, like anastrozole (Arimidex), letrozole (Femara), and exemestane (Aromasin)

    • Fulvestrant (Faslodex)

    • Tamoxifen (Nolvadex)

    Hormonal therapy is sometimes combined with another type of treatment. Learn more about testing for ER and PR and hormonal therapy for breast cancer.

  • Human epidermal growth factor receptor 2 (HER2). HER2 is a protein found in all breast cells, but at different amounts. When a breast cell has an abnormally high level of HER2, it can drive breast cancer growth and spread. Testing for HER2 helps doctors know if a cancer can be treated with anti-HER2 treatments. These are treatments that can stop HER2 from helping tumor cells grow and spread. Currently approved treatments include the following:

    • Trastuzumab (Herceptin)

    • Pertuzumab (Perjeta)

    • Lapatinib (Tykerb)

    • Trastuzumab emtansine (TDM-1; Kadcyla)

There are also a number of other HER2 treatments that are being studied. Learn more about HER2 testing and HER2 therapy.

Other tests used to determine treatment options

Tests that take an even closer look at how the tumor works are commonly used to understand more about a woman’s breast cancer. These tests can help estimate the risk of a cancer coming back after diagnosis, called a recurrence. They are used to help decide if a person would benefit from hormonal therapy, radiation therapy, chemotherapy, other types of treatment, or a combination of treatments for breast cancer.

Recommendations for using tests to predict a recurrence

The ASCO recommendations for when to use the tests listed below to find out whether a person might benefit from adjuvant systemic therapy depends on the ER/PR and HER2 results and whether the cancer has spread to the lymph nodes. These tests look at the genes in a tumor or the proteins made by the tumor to estimate the risk of recurrence.

  • For people with ER/PR-positive, HER2-negative breast cancer that has not spread to the lymph nodes. The following tests may be considered.

    • Oncotype DX

    • EndoPredict

    • Breast Cancer Index (BCI)

    • PAM50

    • uPA and PAI-1

  • For people with HER-2 positive or triple negative (ER/PR-negative and HER2-negative) breast cancer. The tests listed above have not yet been shown to be useful for predicting risk of recurrence in people with these types of breast cancer. Therefore, none of these tests are currently recommended for these tumor types. Your doctor will use other factors related to the breast cancer to help find your treatment options.

  • Tests not recommended.The following tests are not recommended for people with any type of breast cancer because there isn’t yet enough evidence that they can accurately predict the risk of recurrence:

    • MammaPrint

    • Mammostrat

    • Immunohistochemistry-4

    • Circulating tumor cells

    • Tumor-Infiltrating lymphocytes

    • Ki67

    • Tests to choose a specific type of hormonal therapy or chemotherapy

What This Means for Patients

If you have been diagnosed with early-stage breast cancer, one of the first steps is to test the tumor for ER/PR and HER2 and find out if it has spread to the lymph nodes. The results of these tests will help your doctor choose the best treatment options for you. If the cancer is ER/PR-positive, HER2-negative, and has not spread to the lymph nodes, other tests to help predict the chance of recurrence may be recommended.

These test results will help your doctor estimate how likely it is that the cancer will return if you do not have additional treatment after surgery. These test results are not the only factor your doctor considers when presenting your options for treatment.

Talk with your doctor about the tests recommended for you, including how the results will be used.

Questions to Ask the Doctor

To help you learn more about biomarker testing for breast cancer and how the results affect treatment, you can ask your doctor these questions:

  • What is the ER/PR and HER2 status of the breast cancer? What does this mean?

  • Has the cancer spread to the lymph nodes?

  • Do you recommend a test to predict my risk of recurrence? If so, which one and why?

  • How are these tests performed?

  • What do the results of these tests mean?

  • How will the results affect my treatment and treatment options?

  • What other factors affect my treatment options?

  • What treatment do you recommend and why?

Helpful Links

Read the entire clinical practice guideline at www.asco.org/guidelines/earlybreastmarkers

Guide to Breast Cancer

Tumor Marker Tests