As this blog focuses on reviewing scientific papers describing biomarker discovery, validation and clinical use, we felt that it was time to pause and review some biomarker basics.

What is a biomarker? A biomarker can be objectively measured to assess a biologic process, a disease process, or a response to a treatment or lifestyle change.1 Almost anything that can be measured offers potential as a biomarker. This blog deals with biomarkers discovered and detected by proteomic and metabolomic technologies such as immunoaffinity and mass spectrometry, but biomarkers can also be discovered, detected and measured using genomics, clinical history, and imaging.

What do they do? Biomarkers can indicate the likely course of a disease. They can also predict whether someone is likely to respond to a certain drug. Some biomarkers can be both prognostic and predictive. In addition, the discovery of new biomarkers is helping us to define the chemical pathways of both normal processes and disease processes.

A phenomenal amount of research is being conducted in this area. Biomarkers are being investigated in just about every disease and disorder known. Novel biomarkers are being discovered on a daily basis and known biomarkers are being tested in different populations and for new disease areas. To give you an idea of scope, almost a quarter million research papers2 describing biomarkers have been published in the peer-reviewed scientific press to date, and there are still many more on the way.

The biggest challenge? Despite the fact that there are thousands of potential biomarkers, very few will ever make it into the clinic as tests. As with all tests, biomarker tests must meet rigorous criteria.3 First, the test must be able to consistently and accurately detect the biomarker in a target population. The quantitative value of the biomarker should discriminate between normal and disease states, or disease progression or regression. If we can detect a biomarker, what action should be taken? There must be scientific evidence or a rationale that suggests that measuring a biomarker can help us make decisions regarding treatment and ultimately change a disease course. Finally, the biomarker must meet the criteria for clinical utility: will the test have an actual impact on clinical practice? Few biomarkers meet all of these criteria.

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What have we learned? The more we understand the chemical processes in the body, the closer we are to developing therapeutic strategies to interrupt them or set them on the right course again. Biomarkers have taught us that certain diseases, such as cancer and diabetes, are very diverse, and that different processes are at work in different individuals with the same disease. Breast cancer is a good example. People with breast cancer do not all have the same type of tumor. Different tumors express different biomarkers that we can use to judge outcome and to prescribe individualized treatments.

Finally, we’ve learned that in complex diseases, no single biomarker tells the whole story. Researchers are now evaluating biomarkers in various combinations, and in the future, we will likely see panels of multiple biomarkers for a particular disease. As we gather more information from biomarkers, we will be able to diagnose and treat people with greater accuracy.

Many excellent biomarker resources exist. Check out the Tumor Markers Fact Sheet by the National Cancer Institute: http://www.cancer.gov/about-cancer/diagnosis-staging/diagnosis/tumor-markers-fact-sheet

References

  1. Adapted from: Biomarkers Definition Working Group. Biomarkers and surrogate endpoints: preferred definitions and conceptual framework. Clin Pharmacol Ther. 2001 Mar;69(3):89-95.
  2. Using the search term “biomarkers” pulled up almost 740,000 titles on http://www.ncbi.nlm.nih.gov/pubmed on October 30, 2015.
  3. Teutsch, Bradley, Palomaki, et al. The Evaluation of Genomic Applications in Practice and Prevention (EGAPP) Initiative: methods of the EGAPP Working Group. Genet Med 11 (1): 3-14 (2009)