Tumor markers are proteins found in the blood or urine when cancer is present in the body, according to the American Cancer Society. Doctors order lab tests on patients' blood to test for the presence of tumor markers if some type of cancer is suspected. Some tumor markers are specific to one type of cancer while other markers are associated with more than one type.
CA 125 Test
A CA 125 test determines a patient's blood level of the protein CA 125, which is also called cancer antigen 125, according to the Mayo Clinic. Doctors recommend a blood test for the CA 125 tumor marker to check for ovarian cancer in women who have a high risk of developing this disease based on family history. The CA 125 blood test is also useful as a way of checking on the condition and treatment of women who have been diagnosed with ovarian, endometrial or fallopian tube cancer. Endometrial cancer starts in the lining of the uterus.
The normal blood level for CA 125 is less than 35 units per milliliter. A woman who has not been diagnosed with cancer and who has a CA 125 level that is higher than normal may have ovarian, endometrial or fallopian tube cancer, according to the Mayo Clinic. The patient's doctor will do further tests to confirm the diagnosis.
Alpha Fetoprotein
According to Medline Plus, a website of the National Institutes of Health, alpha fetoprotein is a protein that is manufactured by the liver and by the yolk sac of a developing fetus. For men and for women who are not pregnant, normal blood levels of this protein are less than 40 micrograms per liter. Doctors use the alpha fetoprotein blood test to aid in the diagnosis of liver disorders and to check for certain types of cancer. Patients whose blood levels of this protein are above normal may have cancer of the testes, ovaries, stomach, pancreas, or liver, or they may have cirrhosis of the liver, according to Medline Plus.
Prostate-Specific Antigen (PSA) Test
Prostate-specific antigen is a protein made by the cells of the prostate gland. The prostate-specific antigen test determines the concentration of this protein in the blood, according to the National Cancer Institute. The prostate-specific antigen test has been approved by the U.S. Food and Drug Administration as an aid in detecting prostate cancer in men over the age of 50. When doctors use this test in conjunction with a digital rectal exam, they may detect prostate cancer in men who do not yet have symptoms of the disease. While a normal blood level for prostate-specific antigen has not been defined, doctors think that as blood levels rise, so does the probability of prostate cancer.
The prostate-specific antigen blood test has been surrounded by controversy because this test can detect minor cancers that may never need treatment. In this instance, patients may be needlessly subjected to the risks of a follow-up prostate biopsy and cancer treatments, such as surgery and radiation therapy.
