What’s a Biomarker, and What Does It Say About Your Health?

This piece originally appeared on katiecouric.com. 

We rely on healthcare providers to tell us how our bodies are doing, but how exactly does a doctor know what our bodies need? Yes, we know that doctors spend a lot more time in school than most of us, and that they can order a battery of tests to understand what’s going on inside our cells. But when it comes to making recommendations, doctors might be relying on a different set of factors from blood tests or bone scans.

We’re talking about biomarkers, which represent a broad range of measurable characteristics of the body. They can be as common as blood pressure or heart rate, and as small as molecules found in bodily fluids or tissue. Biomarkers help doctors identify underlying conditions or diseases, such as cancer, and can be useful before, during, and after a diagnosis.

But how do biomarkers help inform healthcare decisions, especially when it comes to cancer? Here’s how they work.

Susceptibility and Risk

Biomarkers can be stellar predictors of the future: Doctors can use them not just to understand how healthy you are in the moment, but your chances of developing illness later down the road. These special “crystal ball” biomarkers are called susceptibility, or risk, biomarkers and they provide a better understanding of a person’s long-term health forecast.

Even if you didn’t immediately recognize the term, you likely already know about a few common biomarkers, including the BRCA gene. Mutations in the BRCA1 and BRCA2 genes are risk biomarkers, and may be used to determine a person’s predisposition to developing breast cancer. About 50 out of 100 women with a BRCA1 or BRCA2 gene mutation will develop cancer by the time they turn 70 years old, so knowing whether you have the BRCA gene mutation is crucial for your future health. Depending on your risk, your doctor might suggest genetic testing to determine if you carry the gene.

Looking for susceptibility/risk biomarkers may help to get ahead of a disease by guiding lifestyle decisions or informing preventative measures. After all, knowledge is power, and the more you know about your body, the better chance you’ll have at staying healthy.

Screening and Diagnosis

Diagnostic biomarkers detect the presence of a disease or medical condition. Thanks to these biomarkers, healthcare providers are able to catch diseases such as cancer in earlier stages, when they’re more treatable.

One type of diagnostic biomarker that may indicate that you have colon cancer can be found in your stool, which is why getting regular colon cancer screenings is crucial. If you’re over 45 and at average risk for colorectal cancer, your doctor might have talked to you about Cologuard^®. This at-home colorectal cancer-screening test looks for biomarkers in the stool to detect signs of precancer or cancer.

Another form of cancer testing, known as a liquid biopsy, screens for biomarkers in the blood that are released from cancer cells. These tests may help to find cancer at earlier stages, offering a critical tool in getting ahead of the disease. 

Monitoring

Many of us notice each and every change in our bodies — from a fresh freckle to a new aching joint. If you notice a new mole, you might keep track of its daily progression. That’s basically how doctors use monitoring biomarkers — to watch for any changes in a patient at risk of a disease.

Monitoring biomarkers are assessed repeatedly over time. Watching a patient’s blood glucose levels yearly, for example, allow physicians to monitor for diabetes. Adults may also have their cholesterol levels checked if there is a concern for high cholesterol.

These biomarkers are particularly important for people who are receiving or recovering from cancer treatment. By tracking monitoring biomarkers, physicians can see how a patient is progressing.

Prognosis

In 2022, an estimated 1.9 million people were diagnosed with cancer in the United States. For those facing a diagnosis, understanding the likely path of the disease may determine the next steps. That’s where prognostic biomarkers come in.

These biomarkers help doctors to make an educated guess as to what might happen in the future, like whether a disease will progress, or if a patient might have a disease recurrence.

We’ve already discussed BRCA1 and BRCA2 gene mutations as risk biomarkers, but these mutations can play a role post-diagnosis, too. Mutations in the BRCA gene are used to determine the likelihood of a second cancer occurring in women with breast cancer.

Predictive

Before prescribing a medication or recommending a treatment to a patient, physicians might use predictive biomarkers to get a sense of how likely it is that the patient will benefit from that treatment.

For breast cancer patients, tests like the Oncotype DX Breast Recurrence Score^® use tumor tissue to help identify which patients will benefit from chemotherapy, based on their risk of disease recurrence. 

These biomarkers may allow doctors to personalize care by identifying which patients will benefit the most from a particular treatment, and how well that treatment might work. For those facing a cancer diagnosis, biomarker testing is helpful in determining the right treatment options based on their unique cancer type.

Response

While predictive and prognostic biomarkers are used prior to taking action, response biomarkers are used to understand a person’s response during or after treatment.

These are perhaps best known for their use in clinical trials, when scientists want to understand if a new drug or treatment is effective. For example, when researchers are developing new antibiotics, biomarkers may help determine how frequently doses should be delivered. And for individual patients, response biomarkers may help measure if a prescription is working, or if doctors should pursue other treatment avenues.

Safety

Protecting the patient is an important part of medical practice — and some treatments meant to help can even harm you. That’s where safety biomarkers come in: They can help determine if a patient is at risk of developing negative side effects from a drug or exposure, almost like an allergy test. Utilizing these biomarkers could have the potential to predict toxicity from chemotherapy or other treatments.

Biomarkers give doctors the tools they need to understand a patient’s health every step of the way. Whether or not you’re aware of it, your body is constantly providing information about your current and future health. Luckily for us, technology helps doctors understand that info, in order to keep you safe.