What are biomarkers?
More and more, cancer care is evolving with treatments designed to target the genetic or molecular makeup of a cancer. That’s where biomarkers come in.
This term covers a much broader category and can include genes, gene mutations, proteins or other substances that can be measured in blood, tumor tissue or other body fluids.
Why collect and analyze these signals? They provide crucial information about a patient’s health.
Biomarkers aren’t limited to cancer but often provide key insights regarding a person’s cancer (or their risk of it); they can also inform treatment decisions and predict prognosis and/or recurrence. Some can even tell if a patient will respond to a treatment or not, saving them from unnecessary side effects and ineffectual therapies.
What’s tricky for many, especially those new to the world of cancer, are the various terms used to describe biomarker testing.
Doctors might refer to it as tumor testing or tumor genetic testing or tumor subtyping or genomic profiling or sequencing. They might also mention molecular profiling or molecular testing, somatic testing or next generation sequencing, or NGS.
Hunter said biomarkers are the answers you get to “a lab test, an imaging test, any test to check on the status of the tumor. It’s a biological metric that answers a question. It could be a blood draw or even a scan.”
Biomarkers can even be a combination of test results, she said.
“I would call Oncotype Dx a biomarker test,” she said. “It’s a combination assay that looks at gene expression and DNA sequencing to answer the question, ‘Should I give this patient chemotherapy?’” Other tests that look for breast cancer biomarkers include Mammaprint and Prosigna; another test, Cologuard, looks for biomarkers of colorectal cancer.
Chiorean said biomarkers often reflect molecular signatures or profiles.
“We do a biopsy or identify tumor DNA from a blood sample and then we sequence it to look for mutations,” she said. “Chemotherapy will kill indiscriminately, but checking the genetic signatures and profiling with next-generation sequencing (NGS) tells you what type of mutations are present in the tumor. This is essential to determine what treatment options are unique to the tumor.”
Useful biomarkers in breast cancer include ER/PR status, HER2 protein expression, Ki-67 (a cell proliferation biomarker) and various genetic mutations including ALK, ATM, CHEK2, PTEN, BRCA1/2 and others. EGFR, short for epidermal growth factor receptor, is a common biomarker in non-small cell lung cancer. BRCA1 and BRCA2 are biomarkers for prostate, pancreatic, ovarian and breast cancers. And there are many other assays, molecular tests and scans that produce additional useful biomarkers.
Chiorean said molecular tests allow clinicians to “offer patients many more treatments.” But not all cancers have consistent, reliable biomarkers to inform treatment or reveal the aggressiveness of the disease.