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What to Ask Your Doctor about Biomarker Testing

A key part of understanding biomarker testing is how it relates to your own diagnosis, treatment and survivorship. Here we will explore important questions to ask your healthcare team, no matter where you are in your breast cancer journey, and how to use that information to empower your own care and decision-making experience. Dr. Bora Lim and patient advocate Miranda Gonzales take a deep dive into this conversation.

What are some other words my doctor may have used to describe biomarkers?

In breast cancer, biomarkers can be simply defined as genes or proteins that determine or define what type of breast cancer you have. As you may have learned in our earlier biomarker resources, biomarkers can be genomic (looks at the sequence of all genes in a tumor to determine how cells may change over time), genetic (gene mutations inherited in your DNA at conception) or somatic (a non-inherited mutation to cells some time after conception). Examining each piece of this puzzle gives a full picture of your breast cancer subtypes and how they can best be treated and targeted.

For those newly diagnosed, are there tests I should request or ask about in addition to the standard ER/PR/HER2 testing?

It can be overwhelming when you are first diagnosed to take in all of the information and digest your pathology report. Your doctor will explain your estrogen-receptor and progesterone-receptor status, as well as whether your breast cancer is considered HER2+ positive. These important tests are key to determining your treatment plan.

You can also ask about your Ki-67 levels, which is a protein expressed at higher levels when cancer cells are growing and multiplying fast. As cancer treatments are becoming more and more personalized, biomarkers like Ki-67 help determine the course of treatment and a person's likelihood of recurrence. Tests like Oncotype DX or MammaPrint can also inform a patient on their likelihood of recurrence and possible benefit of more aggressive therapy. On the other hand, if these tests show a low likelihood of recurrence, a patient may follow a more conservative treatment plan that lessens unnecessary side effects.

If I have already completed my breast cancer treatment, what should I know about additional testing as a survivor?

If you are post-diagnosis and finished initial treatment/care, make sure to locate or request a copy of your pathology reports. It is important to have a record of your diagnosis details for future reference or in case you change doctors.

As research progresses, survivors will have more and more access to screening tests and monitoring of recurrence. One exciting development is the examination of circulating tumor DNA (ctDNA and circulating tumor cells), which is taken via a blood sample. ctDNA shows “hidden” cancer cells that may have survived prior treatments like chemotherapy and radiation. If there are remaining cancer cells or particles of cancer cells that are shown to be circulating in the body, this may indicate a higher risk of breast cancer recurrence and as a result, a need for a comprehensive monitoring or treatment plan.

If I have a breast cancer recurrence, what should I ask my doctor about re-testing for biomarkers?

Breast cancer can come back in one of two ways: 1) Your initial breast cancer was successfully treated, but you develop a new breast cancer or 2) Cancer cells from your prior diagnosis found a way to survive and have now re-surfaced.

In both scenarios, it is important to retest your biomarkers. A new case of breast cancer can certainly come back as a different subtype(s) from before. And for those cells that lingered, 20-30% of the time they change types and may have mutated further in order to survive.

How do I self-advocate for the most personalized treatment options? What resources are available to make sure I know all of my testing and treatment options?

In an ideal world, all patients diagnosed with breast cancer would receive care at a comprehensive cancer center. However, even if you live in an area with many options, often insurance or other logistics determine where you have your treatment and appointments. The good news is that more and more community practices have a dedicated breast specialist on their oncology team and/or consult with other experts when determining a patients’ treatment plan and care.

No matter where you receive your care, they may have dedicated resources and education on treatment and testing options specific to breast cancer types. You may also look at reputable sources like,, and the Breast Cancer Research Foundation. Large cancer centers like MD Anderson Cancer Center, Memorial Sloan Kettering Cancer Center and Dana-Farber Cancer Institute also have extensive educational pages on their websites.

Remember that it is always your right to get a second opinion and ask more questions. If you do not feel you are getting the answers you need or would just like to confirm your treatment decisions with another oncologist, ask for referrals from others in your community. Your doctor should be open to you seeking a second opinion, and many will seek out advice from their colleagues on their own.

You may be recently diagnosed or a long-term survivor or living with metastatic breast cancer. No matter what phase of breast cancer you are experiencing, biomarkers play a very important role in treatment and survivorship. In recent years, this process has become more personalized, and the future of breast cancer shows even greater promise than before.