Internal cancers require an extension of observation through endoscopes, x-rays, magnetic resonance imaging, and ultrasound. Laboratory tests, such as the Pap smear, and occult blood testing of the feces have also proven helpful for some of these cancers. However, concerns regarding effectiveness and yield play a particularly important role in decisions to screen for cancers not easily amenable to earlier detection through physical examination in asymptomatic individuals. The performance of these tests is usually measured in terms of sensitivity, specificity, and positive and negative predictive values. Physician judgment is needed in such circumstances to determine the most appropriate application of available screening methods.
Prudence dictates increased vigilance in the higher-risk populations.
This primarily means that the high-risk person is identified, is counseled appropriately, and regularly undergoes the screening procedures of known benefit. The relation of stage to survival and mortality is the basis of clinical cancer management. It is the major factor in prognosis, in the determination of treatment, and in the evaluation of end results. These elements are then grouped into Stages 0-IV according to their association with survival. Classification of cancer by prognostic factors has developed through the extensive study of thousands of cases followed for many years.