Tumor marker test
A tumor marker test examines the blood for signs of the original cancer, such as prostate-specific antigen (PSA) for prostate tumors.
Tumor markers are substances (proteins) either released by cancer cells into the blood or urine or substances created by the body in response to cancer cells. Tumor markers are used to evaluate how well a patient has responded to treatment and to check for tumor recurrence.
Tumor markers are useful in identifying potential problems, but in most cases they must be used along with other tests for the following reasons:
- Cells other than cancer cells also produce tumor markers. People with benign conditions may also have elevated levels of these substances in their blood.
- Not every person with cancer has tumor markers.
- Some tumor markers are not specific to any one type of cancer.
- Sometimes, as the cancer becomes more malignant, it stops producing tumor markers, making it appear that the tumor has shrunk.