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Testing and Precision Medicine

Medical Review:Evelyn Robles-Rodriguez, DNP, APN, AOCN

Article: https://www.lbbc.org/about-breast-cancer/testing

In breast cancer precision medicine, testing can include:

  • Screening tests based on your unique risk factors
  • Genetic tests for inherited mutations that can lead to breast cancer
  • Diagnostic tests based on specific symptoms
  • Biomarker tests that can help match cancer cell features to effective treatments
  • Follow-up tests to check for signs of recurrence or cancer spread

Wherever you are in your health experience, read our guide below to learn about tests that can help you and your doctor create an effective care plan for your unique situation.

Personalized medicine for breast cancer: What you need to know

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In this video, experts Evelyn Robles-Rodriguez, DNP, APN, AOCN and Generosa Grana, MD, FACP guide you through the complex world of genetic and genomic testing. Learn:

  • The differences between genetic testing for an inherited mutation and genomic testing
  • How these tests are used in different stages of breast cancer
  • How the tests can help you or your family

Also, you'll receive practical tips on how to become an advocate and a shared decision-maker in your care.

Testing for people at high risk

If you have never been diagnosed with breast cancer but are concerned that you could be at increased risk, it’s important to talk with your doctor.

Your doctor may recommend genetic counseling for many reasons, such as:

  • Having a close family member who was diagnosed with breast cancer at age 50 or younger
  • Having a close family member who was diagnosed with ovarian, pancreatic, or certain prostate cancers
  • Having a male relative who was diagnosed with breast cancer
  • Being of Ashkenazi Jewish ancestry

A genetic counselor can:

Not everyone at increased risk has an inherited genetic mutation. No matter what your genetic test results are, you and your doctor will talk about your individual risk level and steps you can take to reduce your risk. These steps include a regular screening plan.

A screening plan may include:

If an abnormality is detected on a mammogram, your doctor may recommend:

  • A breast ultrasound to get additional images of breast tissue
  • A biopsy that removes a tissue sample to check for cancer cells

People at increased risk for breast cancer who have never been diagnosed sometimes use the term previvor to describe themselves. To learn more about how previvors can manage risk, visit At high risk for breast cancer.

Tests after a new breast cancer diagnosis

If imaging tests such as mammogram and ultrasound show a suspicious area of breast tissue, your doctor may recommend a biopsy to remove a sample for further testing.

After a biopsy, the tissue sample is sent to a lab, where it is examined by a doctor called a pathologist. If breast cancer cells are found, the pathologist determines the stage of the cancer.

Biomarker testing can find out more about the cancer and what treatments might be effective. These tests may include:

The cancer’s hormone receptor and HER2 status will appear in your pathology report. Your pathology report includes information about the cancer’s unique features, including the stage, hormone receptor status, HER2 status, and other characteristics.

After you and your doctor review your pathology report together, your doctor may recommend more tests that can help you decide on a treatment plan:

  • In some cases, CAT scans, PET scans, or bone scans may be recommended after a biopsy to help confirm breast cancer stage.
  • Blood chemistry tests can check your kidney and other bodily functions to make sure certain treatments will be safe for you.
  • For early-stage breast cancer, there are genomic tests that can tell if breast cancer is likely to come back (recur) and how the cancer may respond to certain treatments.
  • For metastatic (stage IV) breast cancer, next-generation sequencing (NGS) tests can confirm whether the cancer has a non-inherited genetic mutation that can be matched to certain treatments.
  • If you are diagnosed at age 65 or younger, or if you are diagnosed at age 66 or older and meet certain guidelines, the American Society of Clinical Oncology (ASCO) recommends genetic testing for inherited mutations such as BRCA1 and BRCA2. People who test positive for a high-risk inherited mutation may be eligible for certain treatments, plus additional follow-up screening to reduce the risk of a new cancer. The first step is meeting with a genetic counselor. A genetic counselor can work with you to:
    • Review your family health history
    • Explain why testing could be helpful
    • Order the test
    • Review the results with you
    • Discuss next steps
    • Help you share your results with family members

If you have questions about the accuracy of your diagnosis, you have the option to seek a second opinion from a different cancer center. Most health insurance covers a second opinion visit, and your doctor’s office staff can help you with the process.

Visit Recently diagnosed for more resources, including:

  • Preparing for treatment
  • Talking with your healthcare team
  • Finding emotional support
  • Paying for treatment

Tests for people in early-stage treatment

If you are in treatment for early-stage breast cancer, you may have already had these tests as part of your treatment planning:

Treatment options for early-stage breast cancer include surgery, hormonal therapy, targeted therapy, chemotherapy, immunotherapy, and radiation therapy.

Once you start treatment, your doctor will order regular blood testing for you. These tests are usually performed before each visit so that you can review the results together:

  • Blood chemistry tests can tell how well your kidneys, liver, and other organs are working. These tests can help monitor your body’s ability to handle the effects of some treatments.
  • Complete blood count (CBC) tests check levels of red and white blood cells. Some treatments cause lower-than-normal blood cell counts.

You and your doctor will decide on a regular screening plan to check for signs of a new cancer or a recurrence. Your plan may include:

For information about treatments, side effects, nutrition, exercise, and emotional support, visit In treatment for breast cancer.

Tests for people living with metastatic breast cancer

If you have been diagnosed with metastatic breast cancer (cancer that has moved beyond the breast to another part of the body), different tests can:

  • Confirm where breast cancer has spread in the body
  • Get more information about the cancer
  • Monitor how well a treatment is working against the cancer

Your doctor will make recommendations for imaging tests that are part of the diagnostic workup and may also be part of a regular follow-up monitoring plan. Imaging tests may include:

Blood tests are also a part of diagnosis and monitoring:

  • Blood chemistry tests look at your kidney, liver, and other organ functions to make sure certain treatments are safe for you.
  • Complete blood count (CBC) tests check levels of red and white blood cells. Some treatments can lower blood cell counts.
  • Cancer antigen tests check for elevated levels of certain biomarkers, such as CA 27-29 or CEA, that may indicate cancer spread. These tests also help doctors monitor how well a treatment is working.
  • Circulating tumor cell (CTC) tests can check the blood for whole cancer cells that have broken away from a tumor. CTC tests can help monitor:
    • Whether the cancer is growing and/or spreading
    • How well the cancer is responding to treatment

CTC testing to count whole cancer cells has not been shown to help inform decisions about whether to change treatments. Researchers are studying CTC tests to learn more about their ability to find specific biomarkers that may be able to guide treatment decisions.

One CTC test, CellSearch, is FDA-cleared to be used in metastatic breast cancer. Learn more about CTC tests.

If metastatic breast cancer has come back after treatment for early breast cancer, talk with your doctor about having a new biopsy of the cancer. Re-biopsying the breast cancer plus immunohistochemistry (IHC) testing and/or fluorescence in situ hybridization (FISH) testing can confirm if the original hormone-receptor status and HER2 status are still the same. Confirming the status can help you and your doctor choose the most effective treatments.

There are also other important biomarker tests called next-generation sequencing (NGS) tests that look for non-inherited genetic mutations in tumor tissue or in fragments of tumor DNA shed into the bloodstream. ctDNA tests are a type of NGS blood test.

If NGS tests find certain mutations, it may be possible to match the cancer to a specific treatment. For example, if NGS testing shows that the cancer has an ESR1 mutation, it may be treatable with elacestrant (Orserdu).

Ask your doctor about NGS testing:

  • At the time of metastatic breast cancer diagnosis
  • Any time you and your doctor are considering new treatments

After a metastatic breast cancer diagnosis, your doctor may also recommend genetic testing for inherited mutations.  Testing is recommended if you are 65 or younger, or older than 65 and meet certain requirements. There are treatments called PARP inhibitors available for certain people diagnosed with metastatic breast cancer who have a high-risk BRCA1 or BRCA2 inherited mutation.

Your doctor may refer you to a genetic counselor, who can:

  • Discuss your family’s medical history
  • Talk about the benefits of testing
  • Arrange for you to have the test
  • Explain the test results
  • Help you decide what to do next
  • Provide guidance for sharing your results with your family

It’s important to know that if you are concerned about the accuracy of a metastatic breast cancer diagnosis,  you have the right to get a second opinion. Your doctor's office can assist you with the process.  Health insurance usually covers a second opinion appointment.

Follow-up testing after early breast cancer treatment

When you have completed most or all of your treatment for early breast cancer, you’ll talk with your doctor about a follow-up plan. Besides regular doctor visits, tests will be recommended. These may include:

  • Annual mammograms if you did not have bilateral mastectomy as part of treatment
  • Other imaging tests such as ultrasound or MRI, depending on your risk of recurrence or a new cancer
  • Blood chemistry tests to help monitor your kidney, liver, and other organ health after treatment
  • Complete blood count (CBC) tests to check blood cell levels; lowered blood counts can sometimes be a sign of cancer coming back
  • If you have never had genetic testing for an inherited mutation or if you had genetic testing more than 10 years ago, talk with your doctor about whether it might be helpful for you now. These tests can identify more inherited mutations than they could many years ago. The test results can:
    • Help you and your doctor decide whether it might be beneficial to have annual MRIs or other screening that can detect a new cancer early
    • Help your family understand more about any potential inherited cancer risk

You and your doctor will decide if other follow-up tests might be helpful for you.

Visit Post-active treatment to learn more about managing concerns that can come up after treatment, such as:

  • Fear of recurrence
  • Body image
  • Managing long-term side effects

Our Survivorship page can help you find connections after treatment, including support groups and LBBC volunteer opportunities and events.

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