With the massive paradigm shift in cancer therapy to precision medicine, the use of biomarkers and biomarker testing has also rapidly evolved to guide treatment selection. However, the terminology used in genomics is complex and inconsistent, and patient advocacy organizations recommend using a common taxonomy to prevent confusion among patients and providers alike. Nurses spend more time with patients and families than any other member of the healthcare team and can reinforce common language and terminology. As a nurse, here are the terms you need to understand.
What Is a Biomarker?
In the broadest sense, a biomarker is a molecule that can be measured in blood, other bodily fluids, or tissues. A biomarker can be an indicator of normal or abnormal biologic processes, such as in cancer. Traditional biomarkers such as lactate dehydrogenase and prostate specific antigen are simple and inexpensive tests that provide valuable information across the cancer care continuum. Assessing for novel biomarkers via new technologies has allowed for identification of genomic and epigenomic alterations underlying carcinogenesis.
Biomarkers can be classified as somatic (i.e., indicative of the acquired cellular and genomic alterations that drive cancer pathogenesis) or germline (i.e., indicative that the genomic alteration is present from birth and in every cell of the body). Other biomarkers demonstrate appropriateness of immune checkpoint inhibitors, such as PD-L1 expression.
The U.S. Food and Drug Administration (FDA) created the BEST (Biomarkers, EndpointS, and other Tools) resource as a classification system to decrease confusion and to increase consistent use of terms. It categorizes biomarkers as follows:
- Susceptibility/risk: indicates the potential for developing a disease or medical condition in an individual who does not currently have clinically apparent disease or the medical condition
- Diagnostic: detects or confirms the presence of a disease or medical condition or to identify individuals with a subtype of the disease
- Monitoring: measured serially to assess the status of a disease or medical condition or to find evidence of exposure to (or effect of) a medical product or an environmental agent
- Prognostic: identifies the likelihood of a clinical event, disease recurrence, or progression in patients who have the disease or medical condition
- Predictive: identifies individuals who are more likely than those without the biomarker to experience a favorable or unfavorable effect from exposure to a medical product or an environmental agent
- Pharmacodynamic/response: shows whether an individual developed a biologic response to a medical product or an environmental agent
- Safety: measured before or after an exposure to a medical product or an environmental agent to indicate the likelihood, presence, or extent of toxicity
There are a host of biomarkers associated with specific cancer types, disease diagnosis or prognosis, and treatment decisions and monitoring. Some biomarkers are not tumor-specific (also known as tissue- or tumor-agnostic).
Dozens of FDA-approved therapies require biomarker testing in the labeling. Some common biomarkers include:
- BRAF in melanoma, colon, or lung cancers
- KRAS and EGRF in colorectal and lung cancers
- HER2+ amplification in breast cancer
- ALK+ in non-small cell lung cancer and lymphoma
- Germline BRCA pathogenic variants in breast, ovarian, prostate, or pancreatic cancers
- Microsatellite instability-high (MSI-H) and mismatch repair deficiencies in colorectal and other cancers
- NTRK in non-small cell lung cancer, thyroid, colon, pancreatic, breast, or other cancers
Diagnosis, treatment selection, recurrence, and relapse detection is now biomarker driven in many cancers. Oncology nurses must learn the biomarker terminology and classification schemas so they can accurately discuss biomarker results with patients and families.