Biomarkers are measurable indicators of a biological state or condition. They provide insights into normal biological processes, disease progression, or responses to treatments. Biomarkers can be observed through simple measurements like blood pressure or body weight, or through complex laboratory tests of blood, urine, or tissues. They help diagnose, monitor, or predict disease risk.
Understanding Cancer Biomarkers
Cancer biomarkers are specific biological molecules or substances found in tissue, blood, or other body fluids that signal the presence of cancer or provide information about its characteristics. These indicators can originate directly from cancer cells or be produced by the body in response to cancer.
These biomarkers encompass a wide array of biomolecules, including nucleic acids, proteins, lipids, and metabolites. They show different concentrations in individuals with cancer compared to those without the disease. These changes can arise from genetic mutations, alterations in gene expression, or modifications to proteins.
Biomarkers in Cancer Care
Biomarkers are integrated into various stages of cancer care, offering valuable insights that personalize patient management. They allow for earlier identification and intervention, which can improve patient outcomes.
They aid in early detection and diagnosis by helping identify cancer at its initial stages or confirming a suspected diagnosis. Some biomarkers can indicate the potential for developing cancer, while others help differentiate between cancerous and non-cancerous conditions.
Biomarkers also guide treatment decisions, aligning with personalized medicine. They predict how a person might respond to certain cancer treatments, helping doctors select the most effective therapies, particularly targeted drugs.
Beyond initial treatment selection, biomarkers monitor disease progression and assess treatment effectiveness. They track a patient’s response to therapy, allowing for adjustments as needed, and can detect early signs of cancer recurrence. Biomarkers can also predict the disease’s course, offering prognostic information about how aggressive a cancer may become.
Key Examples of Cancer Biomarkers
HER2, or Human Epidermal Growth Factor Receptor 2, is a protein that can be overexpressed in some breast and gastric cancers. The presence of HER2 overexpression or gene amplification guides the use of targeted therapies like trastuzumab, which specifically block the HER2 protein to inhibit cancer cell growth.
BRCA1 and BRCA2 are genes that produce proteins involved in DNA repair. Inherited harmful changes in these genes significantly increase the lifetime risk of developing breast and ovarian cancers, and also elevate the risk for other cancers such as male breast cancer, prostate cancer, and pancreatic cancer. Identifying BRCA mutations influences decisions regarding increased surveillance, risk-reducing surgeries like prophylactic mastectomy, and the use of specific treatments such as PARP inhibitors for those already diagnosed with cancer.
PD-L1 (Programmed Death-Ligand 1) is a protein found on cancer cells and immune cells that helps tumors evade the immune system. Testing for PD-L1 expression helps determine if a patient with certain cancers, such as non-small cell lung cancer (NSCLC) or melanoma, is likely to respond to immunotherapy drugs called immune checkpoint inhibitors. High levels of PD-L1 often indicate a greater likelihood of response to these therapies, which work by blocking the interaction between PD-1 and PD-L1, reactivating the immune system’s attack on cancer cells.
Prostate-specific antigen (PSA) is a protein produced by prostate cells, and its levels in the blood are used for prostate cancer screening and monitoring. While an elevated PSA level may suggest the presence of prostate cancer, it can also be raised by non-cancerous conditions like benign prostatic enlargement or inflammation, leading to false-positive results and potentially unnecessary biopsies. Despite these limitations, PSA testing remains a widely accepted tool for screening and tracking the disease.
Epidermal Growth Factor Receptor (EGFR) mutations are common in non-small cell lung cancer. These mutations drive cancer cell growth, and their detection guides the use of targeted therapies called tyrosine kinase inhibitors (TKIs). These drugs specifically block the activity of the mutated EGFR protein, leading to improved outcomes for patients whose tumors harbor these specific genetic changes.
How Biomarkers Are Tested
The detection of biomarkers involves several laboratory techniques, depending on the biomarker type and clinical question. Blood tests, often called “liquid biopsies,” are a minimally invasive way to analyze cancer-related genetic material or cells circulating in the bloodstream. These tests can detect circulating tumor DNA (ctDNA), fragments of DNA released by dying tumor cells, or circulating tumor cells (CTCs), whole cancer cells that have entered the blood.
Tissue biopsies involve taking a small sample of tumor tissue, typically during a surgical procedure, sent to a pathology lab for analysis. Techniques like immunohistochemistry use antibodies to visualize protein expression, while genomic sequencing methods like Next-Generation Sequencing (NGS) read the genetic code of cancer cells to identify mutations or other alterations.
Other body fluids, such as urine, can also be analyzed for specific biomarkers, depending on the cancer type. These testing methods provide accurate and reliable information about the cancer’s characteristics, guiding treatment decisions and monitoring disease response.