The goal of early detection and screening is the diagnosis and treatment of cancer before it spreads beyond the organ of origin, perhaps even in its preinvasive state. Unfortunately, available early detection and screening techniques pick up many tumors at a relatively late stage in their natural history. As a result, decrements in mortality even with the best available detection modalities are likely to be modest. On the other hand, some early detection and screening techniques identify changes with a low probability of progression to life-threatening cancer, thereby resulting in unnecessary diagnosis and overtreatment. New technologies coming from the field of molecular and cellular biology are able to identify genetic as well as antigenic changes during the early stages of malignant progression. Some of these changes show promise as biomarkers for preneoplastic development or for malignant transformation.
