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Doctor, Why Did You Not Do the CA-125 Test?

By Dr. Peter W. Kujtan, B.Sc., M.D., Ph.D.

This article originally appeared on page 22 in the September 27-28, 2003 issue of
The Mississauga News under the feature: Health & Wellness, Doctor's Corner.
Dr Peter W Kujtan

Sadly, ovarian cancer is one of those diseases that we have no ability to detect early. The CA-125 blood test is vastly misunderstood. I receive at least one request a week to have the level checked. This misperception originates from the land of rampant testing for dollars to our south, and from misinformed Internet testimonials. Ovarian cancer affects 1 in 70 women, and when it does, it is often picked up at the metastatic stage when symptoms occur and survival chances drop. This is a frightening proposition for many women.

CA-125 is a protein found in some cells of the fallopian tubes, uterus, cervix, ovaries and linings of the lungs and abdomen. CA-125 levels can rise during normal menstruation, with pregnancy, endometriosis and even with lung infections. Similarly, these levels may not rise at all during the early stages of ovarian and peritoneal cancer. It has no value as a screening test for ovarian cancer, except in some family groups. However, it is used in monitoring cancer treatment. CA-125 levels are ordered when there is suspicion that an ovarian cancer might be present. These cancers are usually large enough to produce an elevated level. Other testing is still required to confirm the diagnosis. As treatment is administered, the levels are repeatedly measured as a way of determining response.

The most common type of ovarian cancer is an epithelial carcinoma which in time can cause CA-125 levels to rise. The ovaries function to produce eggs and some hormones. To accomplish this, the ovaries are programmed to continuously produce cystic type structures, which normally rupture or involute. There is increased risk for ovarian cancer in women whose close relatives had the disease. Interestingly, multiple pregnancies lower the risk as does using the birth control pill. The pill mimics a pregnancy type state to achieve its function.

As yet, there is no method to detect ovarian cancer at an early stage, unlike the Pap smear test which detects cervical cancer. There are no blood tests yet available which provide early warning signs for ovarian cancer. In Ontario, OHIP declines to cover a CA-125 test ordered for screening. There is an option of paying for it yourself, if this may ease any impending anxiety. During the annual Pap smear test, your doctor will attempt to assess the ovaries by feel. In some people this can pick up abnormalities. Ultrasound exams are commonly employed to evaluate abnormalities. A recent world congress meeting concluded that ultrasounds have no value as a screening tool for ovarian cancer. These "just-in-case" exams ordered for women with no symptoms have a high false-positive rate, and could lead to unnecessary surgery and anxiety. This doesn't offer much comfort for most women, but the best strategy so far is to pay attention to changes in your body and have them evaluated.

Related resources:

CA-125 from Wikipedia.
CA-125 blood test urban legend at snopes.com.
CA-125 at Lab Tests Online.
Facts on CA 125 from MedicineNet.
Cancer antigen 125 (CA125) from Canadian Cancer Society. Why a CA125 test is done. How a CA125 test is done. What the results mean. What happens if a change or abnormality is found.
Tests and Procedures: CA 125 test by Mayo Clinic Staff.
CA 125 - The Ovarian Cancer Test by Dr. E. Brydon, Practicing Gynecological Oncologist, Regina. University of Saskatchewan.
Understanding My CA 125 Test Results. For gynecology oncology patients from University Health Network (UHN).
What is a CA 125 test? CA 125 is a blood test. CA 125 stands for "Cancer Antigen 125". It measures how much CA 125 protein is in your blood.
Why is my oncologist ordering this test? For women who have had cancer, the CA 125 test can check how you are responding to your cancer treatment.
Cancer Antigen 125 (CA-125) from WebMD.
CA 125 blood test from MedlinePlus. How the Test is Performed. How to Prepare for the Test. How the Test will Feel. Why the Test is Performed. Normal Results. What Abnormal Results Mean. Risks.
Cancer Antigen 125 (CA-125). Uses of Cancer Antigen 125 from Patient.co.uk. PatientPlus articles are written by UK doctors and are based on research evidence, UK and European Guidelines. They are designed for health professionals to use, so you may find the language more technical than the condition leaflets.

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