Abstract
The development of a new breast cancer biomarker for early detection is a process that begins with biomarker discovery, followed by a rigorous definition and evaluation of the whole process of biomarker determination (analytical validation). It terminates with the assessment of the impact of the biomarker on clinical practice (clinical validation). A 4-phase scheme for the analytical validation process of the biomarkers for early diagnosis has recently been proposed with the aim of covering the need for standardized operating procedures as well as the need for monitoring and maintaining their quality. As far as clinical validation of biomarkers for early diagnosis is concerned, however, a well established phased approach exists, and guidelines are available for both planning studies and reporting results. Although analytical and clinical validation should be logically linked, often this is not the case in real-word practice, especially in the early phases of biomarker development. This is also the case with breast cancer biomarkers for early detection.