What are Biomarkers?

Biological maker are molecules found in blood, other body fluids, or tissues that are indicators of a normal or abnormal process, or of a condition or disease. These molecules may be produced by the body in response to the presence of a disease or they may be the byproduct of the disease process itself. By measuring specific biological maker, doctors and researchers can gain insight into changes occurring in the body and potentially diagnose disease at its earliest stages.

Types of Biomarkers

There are several main types of biological maker:

- Susceptibility Biomarkers maker help identify individuals who are genetically predisposed to develop a certain disease given certain environmental exposures. For example, mutations in the BRCA1 and BRCA2 genes are susceptibility biological maker for hereditary forms of breast and ovarian cancer.

- Diagnostic biological maker detect the presence or absence of a specific disease. For example, levels of prostate-specific antigen (PSA) in the blood can be used as a diagnostic biomarker for prostate cancer.

- Prognostic biological maker provide information about the likely progression of a disease and can help predict treatment outcomes. High-risk subtypes of breast cancer have unique biological maker that correlate with poorer prognosis.

- Predictive biological maker help identify which individuals are most likely to respond to or benefit from a specific treatment. For example, expression of human epidermal growth factor receptor 2 (HER2) predicts response to HER2-targeted therapies in HER2-positive breast cancer patients.

- Pharmacodynamic biological maker measure the biological response to a medical treatment and help monitor how an individual responds to a therapeutic intervention over time. Levels of HIV RNA in the blood are used as a pharmacodynamic biomarker to monitor response to antiretroviral therapies.

- Monitoring biological maker are used to evaluate patient responses to treatment and to detect recurrence or progression of disease. Measuring levels of prostate specific antigen (PSA) after prostate cancer treatment helps monitor for signs that the cancer may be returning.

Biomarker Discovery and Validation

Discovering new biological maker is a multistep process that often begins with basic scientific research and proceeds through validation in clinical studies. Initial biomarker candidates are first identified in cell culture or animal studies, followed by analysis in human clinical samples. Early phase clinical trials then assess whether the biomarker accurately detects or monitors the disease state of interest. Later phase clinical validation studies prospectively evaluate the clinical usefulness and cost-effectiveness of a biomarker in guiding treatment decisions. Throughout this process, biological maker must demonstrate analytical and clinical validity as well as clinical utility to be adopted into clinical practice. Many biological maker require years of evaluation and study before being recommended for routine use.

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