Screening with tumor markers: critical issues.

Reviewing the literature it would appear that tumor markers have often flattered to deceive. Early promise does not often seem to be borne out in extended trials. Despite apparently high specificity, very few markers are capable of assisting in a screening process. This brief review attempts to put the roles of tumor markers in perspective and explain how their misapplication has led to misunderstanding of their potential value in a clinical context. It also considers the theoretical basis for their use and highlights how misunderstanding of these can lead to flawed studies and application.