Biomarkers to Guide Treatment for Early-Stage Breast Cancer

July 10, 2017

To help doctors provide their patients with the highest quality care, the American Society of Clinical Oncology (ASCO) recently updated a guideline from 2016 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 in a person’s blood, urine, or other body fluids. It can also be found in or on the tumor. A biomarker, sometimes called a tumor marker, is made by the tumor or by the body in response to the cancer. Biomarkers help doctors learn more about each person’s cancer so they can recommend the best treatment options for each patient. Learn more general information about how tumor markers are used to diagnose cancer and guide treatment.

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 certain hormones in the body to grow, so it is important to know this information for each patient. Breast cancer that is called ER-positive depends on the hormone estrogen to grow, while PR-positive means the tumor depends on the hormone progesterone to grow. Testing for ER and PR helps your doctor decide whether a type of treatment called 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)

    • Ovarian suppression, which stops the ovaries from producing estrogen

    Hormonal therapy is sometimes combined with other types of breast cancer 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 unusually high level of HER2, it can drive breast cancer growth and spread. Testing for HER2 helps doctors decide if a cancer can be treated with an anti-HER2 drug. Anti-HER2 treatment stops HER2 from helping tumor cells grow and spread. It may be combined with other treatments, such as chemotherapy. Currently approved anti-HER2 treatments include the following drugs:

    • 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 breast cancer. These tests can help estimate the risk of a cancer coming back after diagnosis, called a recurrence. They are also used to help decide if a person would benefit from hormonal therapy, radiation therapy, chemotherapy, other types of treatment, or a combination of treatments.

Recommendations for using tests to predict a recurrence

Listed below are the ASCO recommendations for when to use different testing options to find out whether a person might benefit from adjuvant systemic therapy. Adjuvant therapy is a term used to describe any treatment given after breast cancer surgery. Systemic therapy is treatment that is delivered through the body’s bloodstream. These tests depend on the tumor’s ER/PR and HER2 results and whether the cancer has spread to lymph nodes. Lymph nodes are tiny, bean-shaped organs that help fight disease. These tests look at the genes in a tumor or the proteins made by the tumor to estimate the patient’s risk of the cancer returning after treatment, called a 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

    • MammaPrint, for those with a high risk of cancer recurrence based on how much ER/PR is in the tumor and how quickly the cancer grows.

  • For people with ER/PR-positive, HER2-negative breast cancer that has spread to 1 to 3 lymph nodes. The following test may be considered:

    • MammaPrint, for those with a high risk of cancer recurrence based on how much ER/PR is in the tumor and how quickly the cancer grows

  • 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 specific types of breast cancer. Therefore, none of these tests are currently recommended for breast cancer that is HER2 positive or triple negative. Your doctor will use other factors to help recommend treatment options for you.

  • 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 shows they can correctly predict the risk of recurrence:

    • 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 cancer has spread to the lymph nodes. The results of these tests will help your doctor recommend the best treatment options for you.

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 you and your doctor considers when deciding among your options for treatment.

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

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?

  • What do the results of these tests mean?

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

  • What other factors affect my treatment options?

  • What treatment plan do you recommend and why?

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