What is a tumor marker?
A tumor marker is a type of substance that occurs in the blood of someone who has cancer. There are different markers for different tumor types that can occur in the blood. Some of these substances only occur in one particular tumor type, while others occur with multiple tumor types. We can test for tumor markers in your blood, urine, cerebrospinal fluid, or tissue biopsies.
The presence of these substances doesn’t prove the existence of a tumor in your body: many of these markers can also occur in other diagnoses, or even in healthy people. Keep in mind that the results alone cannot lead to a diagnosis. Tumor markers can help us diagnose you, but only in combination with other diagnostic tests.
The markers can tell us more about the progression of your illness. We can see if your treatment has been effective, and whether your cancer returned after treatment.