What Is the CA-125 Test?

The CA-125 test looks for certain proteins in your blood. Ovarian cancer can be the reason for these proteins, but other conditions can cause them to be in your blood as well.

This test is also called:

Your doctor may order a CA-125 test if you’re about to start treatment for ovarian cancer. The test will help him determine how active your tumor is now and after your therapy. This will give a pretty good picture of how well your treatment is working. You may have this test done several times during your ovarian cancer treatment.

If you have a high risk for ovarian cancer, your doctor may recommend that you have the CA-125 blood test along with a transvaginal ultrasound on a regular basis. 80% or more of women with ovarian cancer have high levels of CA-125.

But there are many exceptions. About half of women with early stage ovarian cancer have normal levels. Always talk to your doctor about the need for and timing of such testing.

The CA-125 test also may be done if you have a lump in your pelvic area. It will help your doctor figure out the cause of the lump.

What It Can’t Do

Unless you’re at high risk, your doctor probably won’t use the CA-125 test to screen you for ovarian cancer. That’s because not all ovarian cancers cause CA-125 levels to rise. And you also can have higher-than-normal levels of CA-125 without having ovarian cancer. The U.S. Preventive Services Task Force recommends against ovarian cancer screening in women who don’t have symptoms or have a low risk for it.

Other things besides ovarian cancer that can cause your CA-125 level to rise are:

Also, healthy, normal tissue in the cells of the ovaries, pancreas, breast, and lining of the chest and stomach make and release low levels of CA-125.

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Understanding Your Results

A very high level of CA-125 is something the doctor will want to look into, but it doesn’t always mean you have ovarian cancer. One single test result probably won’t be that helpful. A series of results that show changing levels is better when it comes to diagnosing a health condition or problem.

If your levels are high, your doctor may recommend other tests, such as a pelvic or transvaginal ultrasound, to determine the cause.

If you are being treated for ovarian cancer and your CA-125 levels go down during this time, it usually means your treatment is working. If they stay the same or go up, you may need a different type of therapy. Your doctor will discuss your treatment options with you.

Very high levels of CA-125 after you finish ovarian cancer treatment could be a sign that the cancer has returned.

Do You Need a Specialist?

The CA-125 test isn’t perfect, and individual results can be hard to understand. The results for one woman don’t necessarily mean the same thing for another woman.

Because it’s confusing, you may want to talk about your test results with a specialist who has more experience in gynecological cancer. Ask your doctor for a referral.

WebMD Medical Reference Reviewed by Laura J. Martin, MD on November 10, 2018

Sources

SOURCES:

UpToDate.

American Cancer Society. “CA-125 Tests.”

National Ovarian Cancer Coalition: “How am I Diagnosed with Ovarian Cancer?”

Foundation for Women’s Cancer: “Understanding CA-125 Levels.”

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