Tumor markers--prognostic and therapeutic implications for colorectal carcinoma

Molecular prognostic markers are molecules produced by either the tumor or the host (patient) whose expression is associated with the clinical outcome. Three types of molecular markers exist that characterize different aspects of the tumor : host relationship: (1) tumor biology, (2) tumor burden and (3) host response. The first type of marker is measured within the primary or metastatic tumor mass and defines the aggressiveness of the cancer and its ability to respond to therapy. The other two types of markers are usually measured in the blood and assess concentrations of circulating tumor products or cytokines that may be involved in host resistance to the cancer. In this brief review we will define each type of marker, provide examples of their current utility and then describe how these markers may be useful.