By Stephanie Portes-Antoine, BS, Brandel France de Bravo, MPH, and Caroline Novas
Ovarian cancer is a deadly disease because it is rarely diagnosed early. There is not yet an effective, life-saving screening tool for the early diagnosis of ovarian cancer.
When ovarian cancer is diagnosed in the early stage-before the cancer has spread beyond the ovaries-chances of a woman’s survival are very good, with about 93% of women surviving at least 5 years. Unfortunately, only 15% of cases are caught this early, because the symptoms of ovarian cancer are not obvious. For women diagnosed with advanced ovarian cancer, the chances of 5-year survival drop to less than 30%. Given the dramatic differences in survival outcomes between advanced and early onset diagnosis, it is vitally important to detect ovarian cancer early.
Most women whose ovarian cancer is detected in the late stages will have a relapse (usually many times) following their initial treatment, requiring additional treatment. Recent research results have raised questions about whether the most widely used tool to screen for ovarian cancer recurrence in women who were previously diagnosed helps women live any longer. The blood test measures CA125, a protein that tends to be higher among women with ovarian cancer. In 2008, Dr. Vladimir Nosov from UCLA Medical Center and his co-authors reported that elevated levels of CA125 are found in approximately 83% of women with advanced stage ovarian cancer and 50% of patients with stage I disease.
However, other studies indicate that CA125 by itself is not sensitive enough to diagnose ovarian cancer in the very early stage of the disease, before there are there are symptoms. According to Dr. Saundra S. Buys, co-director of the Family Cancer Assessment Clinic at the Huntsman Cancer Institute in Salt Lake City, Utah, CA125 testing “may be appropriate to screen for ovarian cancer in women who have abdominal symptoms, but for women who have no medical symptoms, doing screening for ovarian cancer results in a lot of false-positives.” “False positives are test results that inaccurately indicate the person might have cancer. Dr. Buys based her conclusions on data for women ages 55 to 75 who were participating in a large study called the Prostate, Lung, Colorectal, and Ovarian (PLCO) cancer screening trial.
Many experts hoped that CA125 might be effective to detect relapse among women previously treated for ovarian cancer. However, at the June 2009 meeting of the American Society of Clinical Oncology, Dr. Gordon Rustin reported that women who started chemotherapy early, based on a CA125 test result indicating relapse of ovarian cancer, did not live longer than women who did not begin treatment until symptoms of relapse appeared.
In 2011, Saundra Buys and her colleagues published the results of a randomized controlled trial of more than 78,000 women, which found that using the CA 125 blood test to screen for ovarian cancer doesn’t just prevent women from dying from the disease, it actually is harmful. False positives resulted in many women having unnecessary surgery: 3,285 women received false positives and 1080 of these women underwent biopsy surgery. In 15% of cases, the unnecessary surgery caused serious complications. At the same time, there was no benefit in terms of survival of the women undergoing the test compared to those that did not.
Unfortunately, there are no better screening tools. Research is underway to evaluate whether the CA125 test can be improved or used in combination with other tests.
The bottom line: there is no reason to take a CA125 test. If you have already taken the test and your doctor is recommending treatment based on the results, be sure to get a second opinion from a doctor who does not serve as a consultant to or have other financial ties to the company that makes the test (LabCorp).
References
The National Cancer Institute. Surveillance Epidemiology and End Results. SEER Stat Fact Sheets. Cancer: Ovary. http://seer.cancer.gov/statfacts/html/ovary.html
NCI Cancer Bulletin. Early Chemo to Prevent Ovarian Cancer Recurrence Fails to Increase Survival. June 2, 2009. Volume 6/Number 11. http://www.cancer.gov/ncicancerbulletin/060209/page2
Nosov V., et al. The early detection of ovarian cancer: from traditional methods to proteomics. Can we really do better than serum CA-125? American Journal of Obstetrics and Gynecology.
Reinberg, S. Ovarian Screening Methods Inaccurate. National Women’s Health Resource Center. November 7, 2005. http://www.healthywomen.org/resources/womenshealthinthenews/ovariancancerscreeningmethodsinaccurate
Buys S.S., et al. Ovarian cancer screening in the Prostate, Lung, Colorectal, and Ovarian (PLCO) cancer screening trial: Findings from the initial screening of a randomized trial. American Journal of Obstetrics and Gynecology. November 2005: 193(5): 1630-1639.
Rustin, G.J. and van der Burg. A randomized trial in ovarian cancer (OC) of early treatment of relapse based on CA125 level alone versus delayed treatment based on conventional clinical indications (MRC OV05?EPRTC 55955 trials). Presented at the 2009 American Society of Clinical Oncology Annual Meeting. May 29-June 2nd in Orlando, Florida. http://www.ascov2/Meetings/Abstracts?&vmview=abst_detail_view&confID=65&abstractID=30412
Buys S.S., et al. Effects of Screening on Ovarian Cancer Mortality: The Prostate, Lung, Colorectal and Ovarian (PLCO) Cancer Screening Randomized Controlled Trial. The Journal of the American Medical Association. July 2011; 2011 (616):1.