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Biomarker Testing & Precision Medicine

You probably have a good grasp on the world of biomarkers after learning more about Biomarkers 101 (link) and Biomarkers in Metastatic Breast Cancer (link). Well, we are about to throw another term at you: precision medicine. YSC had the chance to dive into precision medicine and how biomarkers fit in with patient advocate Victoria St. Martin and Dr. Nikhil Wagle.

What is precision medicine and precision oncology?

According to Dr. Wagle, precision medicine is, “the use of information (from a tumor, patient characteristics and clinical history) to tailor therapies [treatment] and improve decision making.” In cancer, it is also called precision oncology. Precision medicine gives healthcare providers the ability to choose the “right drug for the right patient at the right time.” This means that two individuals with similar diagnoses may, for other reasons, receive a different treatment, more treatment or less treatment.

How do biomarkers play a role in precision medicine?

Precision medicine uses biomarker testing to look at the biology of a tumor or patient characteristics from a sample (e.g. blood, tumor tissue, saliva) to find important differences in both a tumor and the individual patient characteristics. By identifying biomarkers, patients are able to receive targeted treatment that may have the best results and minimize short- and long-term side effects. Breast cancer has one of the longest-standing histories of using biomarkers in precision oncology. Testing for estrogen-receptor positive, progesterone-receptor positive and HER2+ breast cancer have been standard of care for many years.

In certain types of early-stage breast cancer a patient may also receive genomic testing like Oncotype DX or MammaPrint. These tests can inform a patient on the likelihood of recurrence (meaning the likelihood of their cancer coming back), and possible benefits of more aggressive therapy. Conversely, if these tests show a low likelihood of recurrence, a patient may follow a more conservative treatment plan that reduces unnecessary side effects.

Similarly, by identifying mutations like PIK3CA in patients with metastatic breast cancer or confirming that a patient has triple negative breast cancer, for example, other targeted treatments like alpelisib (e.g. Piqray) and immunotherapy respectively may work the best. In younger patients who have a higher rate of genetic mutations as it relates to breast cancer, genetic (germline) biomarkers like BRCA 1/2 and PALB 2 can also inform treatment decisions.

Aside from using biomarkers to determine types of breast cancer, how is precision medicine used to predict things like response to treatment?

Healthcare providers have seen for years that not every patient responds in the same way to something like chemotherapy or immunotherapy. There are standard combinations that are frequently used, but one individual may show a large response, while another may not. Currently, there are biomarkers being studied to personalize therapy and help drug development, so that everyone can reach the maximum response.

What are some obstacles and limitations to precision medicine and biomarker testing?

This question can be looked at in two ways- in terms of research and in terms of treatment. For research, our knowledge is only as good as our ability to study patients. Studies need more participants in clinical trials, as well as sharing of specimens and clinical information. Additionally, this participation needs to be diverse and representative of the full breast cancer population. When communities like Black and Latinx survivors are historically left out of research, findings may be biased or not applicable to breast cancer patients as a whole.

As for how to use what we learn through research- education, care and treatment need to be both equitable and accessible in order to be successful. Because of this, education of healthcare providers and patients is important to bring the awareness, accessibility and availability of true precision treatments.

What is the future of precision medicine for breast cancer specifically?

In the case of metastatic breast cancer, researchers are learning more and more about subtypes and, as a result, new targeted drugs and immunotherapies. By gaining more information about an individual's biomarkers, as well as their response to different combinations of treatment, researchers and doctors can continue to identify the treatments that can have the longest success.

In early-stage breast cancer, research is looking at who is at highest risk of recurrence and/or spread and identifies the most effective methods of care and monitoring. Something like a liquid biopsy can be taken from a blood sample and gives a picture of risk.

How can young adults help move research forward, whether or not they have already been diagnosed or completed breast cancer treatment?

Research is strengthened by participation, and the more we understand patterns in biomarkers and treatment, the more impact we will have. Patients are key to moving research forward. Initiatives like Count Me In ( benefit from the voluntary submission of medical records, saliva/blood samples and tumor tissue by cancer patients in the United States and Canada. This information is then made available to researchers to help their own research. Studies, like Count Me In, are voluntary and should give you information on how your data will be used and how you can ask additional questions. YSC is always a resource for you, if you want to know more about what it means to participate in research.

Whether you are newly diagnosed, in active treatment or a long-term survivor, you have and will benefit from advancements in precision oncology. Throughout your diagnosis and care, biomarkers were used every step of the way to ensure you were receiving the most targeted and effective treatment, while also lessening short- and long-term side effects. No matter what phase of your breast cancer journey you are in now, that will continue to be true. The future of biomarkers will find the best treatments for those who need them and predict the best outcomes in follow-up care.