Breast Cancer

What is biomarker testing?

Biomarker testing is a powerful tool that plays a critical role in understanding and guiding treatment decisions for metastatic breast cancer.

In metastatic breast cancer, biomarker tests are often done to look for specific cancer cell features, including:

  • Changes in protein markers: ER: Estrogen receptors, PR: Progesterone receptors, HER2: Human epidermal growth factor receptor 2
  • Changes in tumor cell DNA: AKT1 mutations, ESR1 mutations, NTRK gene fusion, PD-L1 protein expression, PIK3CA mutations, PTEN alterations, RET fusion

Why is biomarker testing important in metastatic breast cancer?

Over time, metastatic breast cancer can evolve, and its biomarkers may change. If you have been diagnosed with metastatic breast cancer, biomarker testing can help you and your healthcare team:

  • Understand more about what may be causing the cancer cells to grow and multiply
  • Choose effective treatments that target specific biomarkers
  • Monitor the cancer for biomarker changes that can help you decide on new treatment options

Researchers continue to work on finding new treatments that target known and new biomarkers.

When to ask your doctor about biomarker testing

Ask about biomarker testing whenever you and your doctor are discussing a new treatment plan, such as:

  • Soon after a metastatic breast cancer diagnosis
  • If cancer progresses (grows or spreads)

Getting tested at these times can help you and your healthcare team understand whether a certain treatment is working well or if the plan should be adjusted. This helps ensure that the treatment plan remains as effective as possible in controlling the cancer.

How is biomarker testing done?

Biomarker tests for metastatic breast cancer can be performed using a biopsy—a procedure that removes a small sample of tumor tissue—or a blood test, often called a liquid biopsy, that can look for DNA in the blood that has been shed by tumor cells.

The tumor tissue or blood is then sent to a laboratory for testing.

Testing Questions

Your step-by-step guide to biomarker testing

Step 1 — Take stock

Metastatic breast cancer biomarkers are highly individual. Understanding the cancer’s biomarker status is an important first step in your journey. This knowledge can help you feel confident and prepared to speak with your doctor moving forward.

Step 2 — Talk

Your doctor may have already had the cancer tested for biomarkers. It’s important to know which biomarker tests have already been performed and which ones are recommended for you. You have the right to know and understand your test results—they are key to understanding your diagnosis and treatment options.

These results are also important if you ever decide to seek a second opinion about your diagnosis or treatment plan.

Step 3 — Test

Your doctor will order testing for all recommended biomarkers. Some testing methods can check for one specific biomarker, and others can check for hundreds of biomarkers at a time. Depending on the type of test performed, it may take one to several weeks to receive results.

Step 4 — Treat

Based on your test results, your healthcare team will talk with you about the most effective treatment options for you, tailored to the specific biomarkers of the cancer and your overall health history.

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Video Series: Biomarker Testing in Metastatic Breast Cancer

Frances's Story

“I believe every test and result has a purpose. Biomarker testing helps guide my treatment and reminds me that there’s always a reason to keep moving forward.”

Frances's Story

When Frances, a 39-year-old mother of three, was diagnosed with stage I triple-negative breast cancer, she turned to faith and family for strength. Genetic and biomarker testing revealed a BRCA2 mutation and PD-L1 expression, guiding a treatment plan that helped her reach no evidence of disease by mid-2023.

A self-described “recovering workaholic,” Frances left her human-resources career to focus on her children, especially her youngest, who has developmental disabilities. Her recovery gave her family time to travel, reconnect, and celebrate everyday moments.

In June 2025, routine imaging revealed nodules in her lungs. Further testing confirmed metastatic triple-negative breast cancer with low HER2 expression, strong PD-L1 positivity, and the same BRCA2 mutation from her initial diagnosis. These results again showed how biomarker testing can shape care—helping her oncologist identify a PARP inhibitor, a type of targeted therapy shown to be effective in treating BRCA-related metastatic breast cancer.

Now 42, Frances continues to focus on faith, family, and advocacy. She encourages others to ask about biomarker testing, understand their subtype, and explore tailored treatment options. A proud Filipina American, she passionately works to open conversations about cancer within Asian American, Native Hawaiian, and Pacific Islander communities.

Kim's Story

“You can still have life after a metastatic diagnosis. After 15 years of living with MBC, knowing I have an ESR1 mutation has opened up more opportunities and lines of treatment for me.”

Kim's Story

In 2003, Kim Builta worked in accounting for her local school district outside Austin, Texas, when she was diagnosed with stage IIIb breast cancer. She continued to work through treatment, lining up holidays with chemo days and managing her two young children, who were 5 and 8, alongside her husband, a coach at a local private school.

Treatment seemed to fly by, as did the five years of tamoxifen she took for her hormone-positive disease. By 2010, bothersome pain in her hip led her to see her primary care doctor, where imaging showed her hip socket was gone. The next day, a biopsy confirmed her breast cancer had metastasized, degrading the bones in her hip and leg. It took highly specialized orthopedic surgeons multiple surgeries over the next seven years to reconstruct her hip, leaving her left leg 3 inches shorter than the right.

For the last 15 years, she has managed progression through several chemotherapies, hormonal therapies, surgeries, and five rounds of radiation. While her oncologist checked biomarkers at each progression, her most recent check in late 2024 revealed an ESR1 mutation. She began an ESR1-targeted medication in February 2025, which has kept her disease stable. 

Lately, Kim has become a more vocal advocate about metastatic breast cancer. What began as a way to communicate efficiently to friends and loved ones on a personal blog has become a mission to complete her memoir by her 60th birthday in 2026. Her experience has given her a lot of confidence in sharing her story, including how important biomarker testing has been to offer her a new line of treatment as she continues to thrive after 15 years since her metastatic disease.

Florina's Story

“I trust my care team to do the right thing, but I’ve learned to ask questions and understand my results. Being part of the decisions about my treatment helps me feel hopeful and in control.”

Florina's Story

Florina was 38 when she was diagnosed with de novo metastatic breast cancer in May 2021. Working as an accountant in New York, she was studying to become a CPA when she noticed lumps under her arm shortly after receiving her second COVID-19 vaccine. She credits the timing with revealing symptoms that led her to seek medical care.

After visiting her doctor, Florina learned she had estrogen and progesterone receptor-positive, HER2-negative breast cancer that had spread to her bones. Biomarker testing confirmed her breast cancer subtype and helped her care team choose the right treatment plan. She has not had additional biomarker testing since, but plans to ask her doctor about it to learn whether new targeted options may be available.

Since her diagnosis, Florina has received several types of treatment that have helped keep her cancer stable. She has also undergone major surgeries but continues to live fully, finding strength in the companionship of her dog, Peanut, and the support of her mother.

Florina’s experience inspired her to leave her accounting career and focus on healing and advocacy. She encourages others to ask about biomarker testing, which can help reveal more personalized treatment paths and bring renewed confidence and hope.

Joy's Story

“MBC patients face hard decisions about their care. Biomarker testing helps alleviate some of that stress because it’s actionable. Any time there is progression, getting a sample is so important because it gives you more options. You’re doing something very specific to help your situation. This type of testing combined with medical research is what keeps me hopeful.”

Joy's Story

On the day COVID lockdowns took effect in 2020, Joy Ragland was blindsided by a stage I, hormone-positive breast cancer diagnosis. A former public school teacher and business owner with her husband, Joy had no family history of breast cancer and was an active, otherwise healthy 42-year-old mom of two. 

Less than a year after finishing treatment, a follow-up MRI in 2022 found a sternum lesion, meaning a diagnosis of metastatic breast cancer (MBC). Joy had just turned 45. A new drug combination kept her disease stable for about 16 months, when the lymph nodes on her left side began showing changes. 

Biomarker testing of that biopsy revealed a PIK3CA mutation, a critical step to choosing a more specific treatment for her cancer. She was on that therapy for 18 months with minimal side effects, and she will soon have radiation to where her lymph nodes were recently removed.

Today, Joy takes the conversation about MBC wherever she goes, leading a local group of metastatic survivors, advocating with healthcare providers, and reviewing grants for new research. 

Joy continues to live a full life with her family, as a small-business owner, and doing her favorite outdoor activities. She is confident that if and when progression comes, biomarker testing is a tool that can open up more options for treatment.

Bethany's Story

“What excites me most about biomarker testing is that it provides more tailored treatment options to my particular cancer and opens doors to more clinical trials with cutting-edge treatments. More treatment options lead to more peace of mind in my cancer journey.”

Bethany's Story

When Bethany, a 34-year-old mindset coach and yoga therapist in Texas, received an unexpected early-stage breast cancer diagnosis, she chose to embrace cancer as a wise teacher.

Five years later, Bethany moved to Colorado, met her future husband, and embarked on a new chapter of life. But chronic back pain signaled something more. Despite initial dismissals from doctors, Bethany persisted in seeking answers. Imaging eventually revealed that her cancer had returned as metastatic breast cancer (MBC), spreading to her bones, liver, and lymph nodes.

Biomarker testing became a crucial part of Bethany’s treatment plan. Her original diagnosis revealed no mutations, but further testing conducted during a clinical trial identified an ESR1 mutation and others. These findings guided her to a targeted therapy, which she remained on for six months, and the identification of additional mutations—FGFR1, MYC, NSD3, and ZNF703—has sparked hope for future treatments and clinical trials.

Now thriving, Bethany recently married, honeymooned in Greece, and finds joy in nature, mindfulness, and gratitude. Cancer is still her guru, guiding her advocacy as she empowers others to make informed decisions about their care, emphasizing the vital role of biomarker testing in opening doors to personalized treatments and brighter possibilities.

Betty

Betty's Story

“Seeking a second opinion was crucial after my misdiagnosis. Though challenging, it led me to my new healthcare team, who reviewed my pathology report and told me I have HER2-positive breast cancer. This guided me to an effective targeted treatment and fuels my advocacy to empower others in their healthcare decisions.”

Betty Sanchez

Betty's Story

Betty is an eight-year metastatic breast cancer thriver who learned early on the importance of advocating for herself. Initially dismissed as an insect bite, Betty's inflammatory breast cancer went undetected until her mother, a retired nurse, insisted on a second opinion.

While this led to a correct diagnosis of metastatic breast cancer, it also prompted immediate, aggressive treatment that took a toll on Betty's physical, emotional and mental state. Fortunately, her journey took a more hopeful turn when she had a second opinion and learned her cancer as HER2-positive, a subtype that responded well to a treatment that was less toxic and more targeted.

Biomarker testing has never been discussed with Betty and she plans to ask her doctor at her next appointment if this is something she should consider.

Now living in Puerto Rico, Betty passionately advocates for patients to be informed advocates for their cancer care. Knowing the sub-type of breast cancer is critical and asking about biomarker testing may reveal other treatment options. Inspired by her journey from misdiagnosis to informed advocacy, Betty empowers others to take an active role in navigating their treatment plans, ensuring they receive the personalized care they deserve.

Megan

Megan's Story

“I speak about biomarker testing so others will explore their options. As a young woman, I'm proof that your journey doesn’t end at diagnosis. It's the beginning of a new phase where understanding your options can make all the difference.”

Megan O'Neil

Megan's Story

At 30, Megan was thriving in her acting career and feeling optimistic about her future when she received a diagnosis of early-stage breast cancer. After chemotherapy, radiation, a double mastectomy, and hormone-lowering medication, she spent nearly five years free from cancer. Then, a sudden chest cramp signaled a devastating discovery: her breast cancer had returned, this time metastatic.

Megan worked closely with her healthcare team to navigate this new chapter. She began with one clinical trial and switched to another after seven months, a move that has proven beneficial. Recently, she underwent biomarker testing to gain deeper insights into her cancer and learned she carries the PIK3CA mutation—information that could offer her more treatment options in the future. Recognizing the significance of this, Megan wishes she had undergone biomarker testing at the time of her initial diagnosis.

Today, Megan continues to be closely monitored by her medical team and feels confident that her recent biomarker testing will help expand her treatment options and guide her path forward. As a passionate advocate, she now shares her journey to educate others facing similar challenges, underscoring the importance of biomarker testing in making informed decisions about care.

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Promote biomarker testing awareness in metastatic breast cancer.

Create your own sign or download and print the sign below, adding your biomarker. Then:

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  • Add the hashtag #NoOneMissed to your social post
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About No One Missed

No One Missed is a community-led campaign driven by LUNGevity Foundation in addition to support from patient advocacy and industry partners. The campaign’s mission is to build public awareness of comprehensive biomarker testing as a critical part of cancer diagnosis and empower patients to discuss comprehensive biomarker testing with their healthcare team. The No One Missed: Metastatic Breast Cancer campaign was launched in partnership with Living Beyond Breast Cancer.

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We envision a future that ensures there’s No One Missed when it comes to biomarker testing in metastatic breast cancer. It’s a critical step to getting a fully informed diagnosis.

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