Telltale proteins in the blood are giving doctors critical early warning of the spread of cancer, new studies suggest.

Cancer cells carry unique proteins on their surfaces that allow the body's disease-fighting immune system to recognize them as abnormal. Now, doctors are finding ways to track down these chemical name tags so they can destroy the cancer before it kills the patient.In a study released Tuesday, Dutch doctors showed that a particular chemical marker, or antigen, known to researchers as CA-125 is the best early sign of ovarian cancer.

In a similar study published last month, researchers at Washington University in St. Louis said another antigen found in the blood can provide early detection of prostate cancer in most men over 50.

Cancer experts have said all the tests need further refinement before they can be considered accurate in consistently determining early development of cancers.