What Are Biomarkers?

Most car owners have experienced the frustration of a blinking “check engine” light at one point or another. While the blinking light signals that something is wrong, only the results of diagnostic tests performed by the mechanic can pinpoint exactly what is going on under the hood.

In the world of medicine, a symptom is like the “check engine” light, alerting a patient that something is wrong but not specifying exactly what the condition is. And that’s where biomarkers come in. They are equivalent to the results of the mechanic’s diagnostic tests, indicating to a doctor what exactly is going on “under the hood.” 

Biomarkers definition

The term “biomarker” actually stands for “biological marker.” So, as the word itself suggests, a biomarker is a measurable marker or sign that tells a medical professional what is taking place inside a patient’s body. There are different types of biomarkers that can be relatively easy to observe, such as a patient’s blood pressure level. Other biological markers can require more complex testing to detect, such as the presence of a protein in a patient’s blood.

Biomarkers in Cancer

Biomarkers have contributed to lifesaving breakthroughs in cancer detection and treatments. They are a critical tool in medical research, as they help scientists get a better understanding of what biological factors may cause different cancers, which investigational drugs are most effective in combating the disease, and how specific therapies should be targeted once approved. 

When scientists study biomarkers in cancer, they are typically observing signs on a molecular level. These markers, which may include proteins and genes, are so tiny that they cannot be seen with the naked eye. Cancer biomarkers may exist in the tumor cells themselves, as well as in other cells of the body that are reacting to the cancer. 

Ovarian Cancer Biomarkers

Biomarkers have played an essential role in the progress against ovarian cancer and continue to be studied by researchers for clues as to how to better detect and treat the disease. Though no reliable biomarker has yet to be discovered that can be used for early detection of ovarian cancer, doctors do use biomarkers to tailor treatment plans and monitor how well the disease is responding to therapy.

Types of Biomarkers

Different biomarkers are used for different purposes. The U.S Food and Drug Administration (FDA) and National Institutes of Health (NIH) have jointly published a glossary defining each biomarker type. Below are brief descriptions and longer biomarker definitions can be found via the FDA and NIH Resource Glossary.   

Diagnostic Biomarker

Just like the results of a mechanic’s diagnostic tests, a diagnostic biomarker indicates the presence of a specific medical condition or disease in a patient’s body. It is a valuable tool that enables doctors to make more precise diagnoses. As mentioned above, no reliable diagnostic biomarker has been found to date for early detection of ovarian cancer. 

Monitoring Biomarker

A monitoring biomarker is a biomarker that is assessed repeatedly over time to keep track of how a disease is progressing, much like continually checking the oil level of a leaky car. Since biomarkers can be measured, a doctor can monitor them over the course of weeks, months, and years to see if a patient’s condition is improving, staying the same or worsening. 

In addition to helping a doctor simply keep watch on the progression of a medical condition, a monitoring biomarker can also tell a doctor how the disease is responding to treatment. This characteristic is particularly valuable because it shows doctors what is working or not working. And that information, in turn, helps doctors provide their patients with more effective therapies. 

CA-125 or “Cancer Antigen 125” is a biomarker for ovarian cancer. It is primarily considered a monitoring biomarker for ovarian cancer, that doctors use to keep watch on how well an ovarian cancer treatment is working for a patient. Since CA-125 is released into the bloodstream, levels are measured via a blood test. 

Doctors often order CA-125 tests as part of a diagnostic workup if they suspect ovarian cancer because CA-125 levels are often elevated in people with ovarian cancer. However, it is important to note that CA-125 misses half of early cancers and can be elevated by benign conditions, such as endometriosis, pregnancy, and uterine fibroids. Thus, it is not considered to be a reliable diagnostic biomarker. Again, CA-125 provides the most benefit when used as a monitoring biomarker. Learn more about CA-125 here.

Predictive Biomarker

Another tool used to tailor a patient’s care plan is the predictive biomarker. This biomarker type can be used by doctors to identify which individuals will respond best to a treatment. Remember that leaky car? Well, perhaps the mechanic is aware of a specific design quirk that is known to cause leaks in this car model. That knowledge will give the mechanic useful insight into how best to fix the leak. In much the same way, a predictive biomarker such as a gene mutation can provide a doctor with crucial information as to whether a treatment is more or less likely to work for a particular patient.

When a patient has been diagnosed with ovarian cancer, a doctor may test for predictive biomarkers, such as BRCA and other cancer-causing gene mutations. Detected through blood or saliva tests, these mutations can signal to a doctor what therapies may work best for that patient.

Susceptibility/Risk Biomarker

Gene mutations can also function as susceptibility/risk biomarkers. These biomarkers can point to the probability of a disease or medical condition developing well before it is present in the body, much like how a manufacturing glitch in a car model can serve as a warning sign that the engine may fail in the future. In the case of BRCA gene mutations, they can alert the doctor to the risk of ovarian or other types of cancers developing. And depending on the risk level for ovarian cancer specifically, the doctor may recommend preventive measures such as removing a patient’s ovaries and/or fallopian tubes. 

Learn more about BRCA gene mutations.

Prognostic Biomarker 

Another biomarker that helps provide a doctor with a more well-defined picture of a patient’s future is the prognostic biomarker. A doctor may use this type of biomarker after the diagnosis of a disease to determine how the patient’s condition may progress without factoring in therapy. A prognostic biomarker gives clues as to the likelihood of a patient experiencing a future recurrence or the development of a new medical condition. 

In the field of ovarian cancer research, there are two proteins that show promise as prognostic biomarkers, though research in this area is on-going. These proteins, which can be found in both healthy and cancerous cells, are called progesterone receptors (PR) and estrogen receptors (ER). The presence of progesterone receptors and/or estrogen receptors in cancerous cells has been linked to higher survival rates for patients living with certain types of ovarian cancer. Read more about this research here. 

Biomarkers in Ovarian Cancer Research

Biomarkers continue to be a promising area of focus in ovarian cancer research, with ongoing studies focused on the potential role of various types in the detection, prediction, and treatment of this disease.  

Learn more about OCRA-funded research into ovarian cancer biomarkers.