The case for early detection

The promise of early detection is that it will identify cancer while still localized and curable, preventing not only mortality, but also reducing morbidity and costs. Cervical cancer is a historical illustration of the promise of early detection; countries with broad screening programmes have markedly reduced disease-related deaths. However, the efficacy and practicality of screening tests for most other cancers remain controversial. The advent of new technologies — including transcript (gene-expression) analysis, genomic DNA-based methods and proteomics — offer many new opportunities for developing biomarker-based tests that are less expensive and more accurate than existing screening tests. To develop and fully evaluate a new screening test requires attention to all phases of biomarker development, including identification of promising biomarkers, production of assays that can detect both clinical and pre-clinical disease, development of tests that combine sensitive biomarkers to achieve greater diagnostic accuracy, and evaluation of the impact of the tests on disease mortality and costs. With many potential biomarkers in the early-detection pipeline, it will be important to develop strategies for evaluating the benefits and costs of biomarker-based tests within a reasonable time frame. The dissemination of screening tests that have been inadequately evaluated can have grave consequences, including invasive follow-up of healthy individuals, morbidity from unnecessary treatment and vastly increased costs to the medical system. Although randomized screening trials remain the ultimate test of screening efficacy in preventing disease-specific mortality, it will be important to develop these and other analytical approaches so that inferences about screening costs and benefits can be made in an efficient and timely fashion. The promise of early detection is that it will identify cancer while still localized and curable, preventing not only mortality, but also reducing morbidity and costs. Cervical cancer is a historical illustration of the promise of early detection; countries with broad screening programmes have markedly reduced disease-related deaths. However, the efficacy and practicality of screening tests for most other cancers remain controversial. The advent of new technologies — including transcript (gene-expression) analysis, genomic DNA-based methods and proteomics — offer many new opportunities for developing biomarker-based tests that are less expensive and more accurate than existing screening tests. To develop and fully evaluate a new screening test requires attention to all phases of biomarker development, including identification of promising biomarkers, production of assays that can detect both clinical and pre-clinical disease, development of tests that combine sensitive biomarkers to achieve greater diagnostic accuracy, and evaluation of the impact of the tests on disease mortality and costs. With many potential biomarkers in the early-detection pipeline, it will be important to develop strategies for evaluating the benefits and costs of biomarker-based tests within a reasonable time frame. The dissemination of screening tests that have been inadequately evaluated can have grave consequences, including invasive follow-up of healthy individuals, morbidity from unnecessary treatment and vastly increased costs to the medical system. Although randomized screening trials remain the ultimate test of screening efficacy in preventing disease-specific mortality, it will be important to develop these and other analytical approaches so that inferences about screening costs and benefits can be made in an efficient and timely fashion.