80% of ovarian tumors secrete CA-125; monitoring levels can help in guiding therapy.
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This test can also be purchased as part of our Women’s WellCheck panel.
PREPARATION: No fasting or other special preparation is needed for this test.
What does this test do?
This test determines the concentration of a protein called CA-125, circulating in the bloodstream.
CA-125 (or Cancer Antigen 125) is a protein normally found in mucus, where it acts as a lubricant, as well as a barrier to infectious agents on the surface of the tissues it protects. CA-125 is secreted by various mucus membranes within the body – for example it is found in the outer membranes of the eye, the lining of the respiratory tract, and in the reproductive organs of women.
Why is this important?
About one in 70 women will develop ovarian cancer in their lifetime. Each year in the U.S. alone over 20,000 women are diagnosed with this disease, and two-thirds of those will die from it.
The reason ovarian cancer is so deadly is in large part due to the difficulty in finding it. The tumors don’t usually cause symptoms until they have become large enough to spread to other sites within the body. Worse, even a thorough, annual gynecologic exam has been shown to be ineffective at finding them.
If detected early however ovarian cancer can be treated. And the earlier it is found, the greater the patient’s chance of survival.
One way to detect even early ovarian cancer is by checking the CA-125 level. The majority (about 80%) of ovarian tumors produce excessive amounts of this protein, and produce elevated levels in the blood.
But because high CA-125 levels are not uniquely specific to ovarian cancer, and because they do not pick up all ovarian tumors, the use of the CA-125 level as a screening test for ovarian cancer is controversial. In fact, some specialists advise against its use in otherwise healthy women.
In ongoing studies by researchers at the MD Anderson Cancer Center however, routine monitoring of changes in CA-125 levels over time have shown promise as a screening tool by identifying “more women with ovarian cancer in earlier stages.”
In women with a known history of ovarian malignancy, routine monitoring of CA-125 levels is recommended, and is widely used to detect any cancer recurrence after treatment.
What do the results mean?
An abnormally high level of CA-125 is very sensitive at detecting ovarian tumors, but it is not specific to ovarian cancer. In other words, a high level does not necessarily indicate the presence of ovarian cancer. There are a variety of conditions – including pregnancy, liver disease, endometriosis, fibroid tumors of the uterus, and diverticulitis – that can also be associated with abnormally high blood concentrations of CA-125.
Likewise, CA-125 levels are not completely sensitive at detecting all ovarian tumors, either, and a normal CA-125 value does not mean the absence of ovarian cancer. Studies have shown that, although about 80% of malignant ovarian tumors cause elevations in this marker, the other 20% of cases don’t affect the level of CA-125 at all.
To ensure an accurate and early diagnosis, any CA-125 elevated level should be rapidly followed up by a visit to a qualified physician for a thorough physical examination, and further testing if warranted.