Yes tumor markers also known as biomarkers can be used as a screening test for cancer. They are substances originated above normal levels in the blood, urine, or body tissue of people affected with cancer. In addition, with other diagnostic tests, testing for tumor markers can point out the occurrence of cancer and help doctors to make right treatment for the patient. If you wish to read detailed information about tumor markers, this pdf http://www.ilexmedical.com/files/PDF/CA125_AXS.pdf will guide you in the right direction. Tumor markers are generally helpful in screening high-risk individuals, confirm the diagnosis, predict prognosis, monitor treatment and guide treatment decisions.