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CA-125 and ovarian cancer

Ovarian cancer is a rare type of cancer. Because early symptoms are subtle and may be mistaken for minor pelvic or bowel discomforts, it is often diagnosed later in the disease process. Sometimes there are no symptoms until the disease has advanced beyond the ovaries.

Current tools for ovarian cancer detection are of little value in routine screening of the general risk population. Women with a mother or sister with ovarian cancer are at higher risk. Risk increases by 5% with one affected immediate family member and up to 7 – 10% when two or more 1st degree relatives are affected.

Use of the CA-125 blood test as a screening tool for ovarian cancer has been given much attention. It was hoped that the test could be used to detect the presence of ovarian cancer, since there is no way to find it early and most women have no symptoms till the cancer is in advanced stages. Unfortunately there are also benign conditions that can also raise the levels of CA-125, so it has not turned out to be a good test for screening.

The trouble with relying solely on elevation of the CA-125 levels for screening is:

Normal levels are found in approximately 50% of early tumors, so it will not always show when there is a cancer present
Serum CA-125 elevation has been reported in both malignant and benign conditions. Elevated in 80% of advanced ovarian cancers, 26% with non-cancerous ovarian tumors, and 66% of women with non-cancerous gynecologic conditions, so it may indicate a cancer is present when it is NOT.
Elevation may be due to other conditions, especially in premenopausal women. These include menstruation, endometriosis, pelvic inflammatory disease (PID), early pregnancy, uterine fibroids, recent abdominal surgery, inflammation in certain major organs – heart, liver, abdominal cavity.

For these reasons the screening tests are not recommended for low risk individuals. The best screening method in low risk women continues to be an annual pelvic examination where the doctor feels the ovaries to detect enlargement. If you are concerned you are in a high-risk group, consult your doctor for more information.

The recommended approach to screening high-risk women includes:

Pelvic exam, including recto-vaginal examination.

CA-125 blood test - it is important to know that in approximately 50% of early tumors, the CA-125 level is normal.

Transvaginal ultrasound – this test uses a probe (a wand-like instrument inserted into the vagina) to produce an image of the ovaries on a monitor screen. Unfortunately, transvaginal ultrasound may demonstrate images that look like ovarian tumors. This requires further surgical inspection – which at times may be unnecessary – because the ovaries may be entirely normal.