The early detection of cancer is the hallmark of increased survival. While imaging techniques are useful in follow-up diagnosis, the future of early detection of cancer resides with tumor markers. There are over 50 tumor markers, either on the market or in clinical trials. Many of these measure a protein that is loosely bound to the tumor cell and is shed into the bloodstream, much like a snake sheds its skin. These tumor markers have, in general, very high false positive and false negative rates, approaching over 50% in some cases. Furthermore the detection of the shed protein frequently occurs late in the disease when treatment options are less effective. Based on the above drawbacks, the American society of clinical pathology does not recommend any tumor markers as reliable.
New methods involve the measurement of the immune response against cancer. When a tumor develops, there are proteins expressed in the cell membranes that previously have not been exposed to the immune system. Antibodies are produced against these cell surface proteins as the first step in a cascade of events that, hopefully leads to tumor destruction by the immune system. The amplification system in this type of detection is enormous. Very small amounts of cancer protein can elicit many antibodies in response. It is this antibody response that we use to quantify the presence of cancer in an individual.
This presentation will summarize most reliable tests for a variety of cancers while focusing on serum and tissue markers.