Validation: a critical step in bringing biomarkers to clinical fruition

Screening is vital to reducing morbidity and mortality due to cancer. A primary cause of poor survival is that many cancers are detected late and often after they have metastasized to distant sites. Therapies, therefore, become challenging for late-stage disease and are not successful for nearly all cancer types. The mortality rates from cancers where screening tools are available are lower than from cancers for which no viable screening tools exist. Even for cancers where screening tools currently exist, there is room for improvement, either in the accuracy of the tests or in increasing widespread use of screening by making the tests less invasive. For instance, despite widely available screening methods that can detect early-stage colon cancer or its precursors, only approximately 40% of newly diagnosed colon cancers are localized. It is a challenge to develop screening tests that are not only highly sensitive but also highly specific, to avoid putting patients through unnecessary biopsies and treatment. Biomarkers have great potential to improve the existing diagnostic accuracies of screening modalities and substitute invasive screening methods with noninvasive methodologies using bodily fluids such as plasma, serum, saliva, urine, etc. Biomarkers are defined by the National Institutes of Health as "a characteristic that is objectively measured and evaluated as an indicator of normal biological processes, pathogenic processes, or pharmacologic responses to a therapeutic intervention." In this commentary, we discuss important measures that could be taken to increase the chances of bringing biomarkers to clinical fruition.