Serum tumor markers. Part I: Clinical utility.

Most tumor markers in current use are glycoproteins that are measured by routine immunoassay techniques. The primary utility of serum tumor markers is for evaluating the effectiveness of therapy in advanced stages of cancer; in addition, they are used for monitoring "cured" patients for cancer recurrence. Regrettably, this latter use has not led to a significant improvement in patient outcomes when a recurrence is detected early. Sensitivity and/or specificity is frequently lacking for most tumor marker tests and their utility as screening tools to detect early cancer is extremely limited. For the most part, decisions based on the concentration of these cancer-associated molecules should always be made in light of the entire clinical picture. A monumental goal in cancer research is to find markers that are significantly more sensitive and specific for early cancer detection, as well as the other uses described herein. In Part II of this series, practical considerations and limitations regarding laboratory testing of tumor markers will be addressed.