This is because many colon cancers do not produce abnormally high levels of CEA in the early stages. This is a tumor marker for ovarian cancer and occasionally cancer of the uterus . It is useful to have this test done when cancer is suspected. However, this test is not always reliable. Some women with ovarian cancer may not have high levels of CA-125.
High levels are common in women with advanced ovarian cancer.
This tumor marker is also used to see how the body is responding to treatment. If the level of CA-125 in the blood goes down after treatment, the disease is probably responding. If the level goes up, the disease may be getting worse. Men with prostate cancer may produce large amounts of this substance. The PSA level can also be slightly high in a man whose prostate gland is enlarged for reasons other than cancer.