What It Is
Tumor markers are blood tests that measure substances, often proteins, that can be produced by cancer cells or by the body in response to cancer, or in some cases produced at elevated levels for other, non-cancer-related reasons as well.
What It Checks
Each specific tumor marker is associated with certain types of cancer. For example, PSA is associated with the prostate, CA-125 is associated with the ovaries, and CEA is associated more broadly with certain gastrointestinal and other cancers. These tests measure the level of the relevant substance circulating in the blood.
Why It's Used
Tumor markers are commonly used to help monitor a known cancer's response to treatment or track for signs of recurrence after treatment, and in some specific situations, as part of a broader evaluation when cancer is suspected. Because many tumor markers can also be elevated for reasons unrelated to cancer, they're generally used alongside other tests and clinical findings rather than as a standalone diagnostic tool.
How It's Done
Tumor marker tests require a standard blood sample, typically drawn from a vein in the arm, similar to most routine blood tests. Depending on the specific marker and clinical situation, testing may be done once or repeated periodically over time to track trends.
Background
The discovery of various tumor markers developed over the course of the 20th century, as researchers identified specific substances that tended to be elevated in association with particular types of cancer. Understanding of tumor markers has continued to expand alongside broader cancer research, and while their role has generally shifted more toward monitoring known cancers rather than initial diagnosis alone, they remain a valuable tool within the broader field of oncology today.