OBOS Home Page
Home  I  About Us  I  Programs  I   Publications  I  Blog  I  Donate Now
Health Resource Center

Unique to Women

The CA-125 Test For Ovarian Cancer

The following article was originally written in response to a widely circulated email claiming that the CA-125 test was an effective ovarian cancer screening test. It is reposted with permission from the authors.

Have you heard about the CA-125 test for ovarian cancer?

Did you know it is NOT an effective screening test for ovarian cancer?

Did you know that the American Cancer Society, the American College of Obstetricians and Gynecologists, the Society of Gynecologic Oncologists, the Canadian Task Force on Preventive Health Care, and many other medical organizations recommend that the CA-125 NOT BE USED as an ovarian cancer screening test?

Why not?  Because it doesn't work!  

Many women have undergone unnecessary surgery (and anxiety) as a result of this test, while others have been falsely reassured by a normal result-while they actually had ovarian cancer. 

Emails circulating online urge women to get the CA-125 test and declare it is the ONLY way to detect ovarian cancer.  Although this information is well-intended, it is inaccurate, misleading and fear-provoking.

CA-125 is NOT an Effective Screening Test for Ovarian Cancer?

ALL the existing studies tell us that CA-125 is NOT a good screening test for ovarian cancer. The CA-125 blood test measures a protein in the blood which is produced by normal cells, as well as by cells from common non-cancerous conditions such as endometriosis, fibroids, benign ovarian cysts, pelvic infections, pregnancy, and normal menstrual periods.  Non-gynecologic conditions such as liver disease and inflammatory diseases  as well as a variety of other cancers also elevate the CA125 levels. 

For a screening test to be helpful, it must detect disease in individuals who feel entirely well, at a time when the disease is in its earliest and most curable stages.   To be helpful, a screening test must be extremely accurate.   For example, even a test that is 99.6% accurate will find 1 woman with the disease, but also will falsely inform 9 women that they have the disease when they do not (false positives).  

For postmenopausal women who have an elevated CA-125 level, most will NOT have ovarian cancer.  The test is even less accurate for women prior to menopause. And, in women who do have early ovarian cancer, (those women we need to find since ovarian cancer is still highly curable) the CA-125 levels will be normal in at least 50%.

If 10,000 women aged 50 - 64 are screened with CA-125 testing for ovarian cancer yearly, 300 women will test positive and require further evaluation. Twenty-four of these women will need surgery, 20 of whom will not have ovarian cancer and, therefore, be subjected to unnecessary surgery with inherent risks and recovery. Only 4 of the 10,000 women will have ovarian cancer.

Similarly discouraging results are found with screening by ultrasound of the ovaries in asymptomatic women.

For Women with a Strong Family History Ovarian Cancer

Testing high-risk women, who have a very strong family history of ovarian cancer, with twice-yearly pelvic ultrasound exams and CA-125 levels is the current standard of care.  Even in the research studies for these high-risk women, the testing has not been shown to be particularly helpful.  If you are at high risk, you should discuss testing with your doctor. 

Symptoms of Ovarian Cancer

Women and their doctors should be attentive to the early signs and symptoms of ovarian cancer that seem to worsen and occur daily for more than 2 weeks.  The most reliable symptoms include abdominal or pelvic pain, bloating, difficulty eating or feeling full quickly, and changes in bowel or bladder habits.

We hope as information continues to be gathered, new more effective methods will be developed that will lead to early ovarian cancer detection

The CA-125 test is not recommended as a screening test for ovarian cancer.

We wish you good health:

William H. Parker, MD
Clinical Professor, Department of Obstetrics and Gynecology, UCLA School of Medicine
Chair, Department of Obstetrics and Gynecology, Saint John's Health Center, Santa Monica, CA

Beth Karlan, MD
Director, Women's Cancer Research Institute and Division, Gynecologic Oncology at
Cedars Sinai Medical Center
Professor, Obstetrics and Gynecology, David Geffen School of Medicine at UCLA

Jonathan S. Berek, MD, MMS
Professor and Chair
Department of Obstetrics and Gynecology
Stanford University School of Medicine
Division of Gynecologic Oncology
Stanford Cancer Center


Screening for Ovarian Cancer: Recommendation Statement
Ann Fam Med U.S. Preventive Services Task Force 2: 260 Annals of Family Medicine 2004;2:260-262

National Consensus on Ovarian Cancer Symptoms

Last revised: January 2008

< Return to Unique to Women Overview






Home I Resource Center I Support Us! I Press Room I Site Credits I Feedback I Contact I Privacy I Site Map