Ovarian cancer is a deadly disease because it is rarely diagnosed early. Despite overly optimistic media stories, 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 diagnosed with ovarian cancer surviving at least 5 years.
1 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%.
1 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 and will need additional treatment.
2 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 usually found at elevated levels in 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.
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Unfortunately, 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,"
4 meaning that many women who do not have ovarian cancer have abnormal test results on the test. Dr. Buys drew her conclusions from looking at data on women ages 55 to 75 who were participating in a large study called the Prostate, Lung, Colorectal, and Ovarian (PLCO) cancer screening trial.
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Many experts hoped that CA 125 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 have treatment until symptoms of relapse appeared.
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iThis is a five-year “relative survival rate.” Relative survival rates compare cancer patients’ chances of survival to women of the same age in the general population. Women whose ovarian cancer was diagnosed when it was still limited to the ovaries were 93% as likely to be alive five years later
as other women their age.
While the CA125 test has been disappointing thus far, it could potentially be useful if combined with other tests. In a study by Dr. Vladimir Nosov and colleagues at UCLA, published in the
American Journal of Obstetrics and Gynecology in June 2009, when CA125 was combined with a panel of three other biomarkers found in the blood, early stage ovarian cancer was detected in 96% of the women who had it.
7 The authors remain cautious, stating that more clinical analysis needs to be done to validate this combination screening test for both early stage ovarian cancer and relapse ovarian cancer. If and only if larger studies find that the results of the CA125 test and test results for the three other biomarkers panel are effective at screening for and detecting ovarian cancer and relapse, these tests could potentially save thousands of lives every year.
References
1. The National Cancer Institute. Surveillance Epidemiology and End Results. SEER Stat Fact Sheets. Cancer: Ovary.
http://seer.cancer.gov/statfacts/html/ovary.html
2. 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
3. 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. September 2008: 199(3): 215-223.
4. Reinberg, S. Ovarian screening Methods Inaccurate. National Women’s Health Resource Center. November 7, 2005.
http://www.healthywomen.org/resources/womenshealthinthenews/dbhealthnews/ovariancancerscreeningmethodsinaccurate
5. 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.
6. 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 indicators (MRC OV05?EORTC 55955 trials). Presented at the 2009 American Society of Clinical Oncology Annual Meeting. May 29-June 2nd in Orlando, Florida.
http://www.asco.org/ASCOv2/Meetings/Abstracts?&vmview=abst_detail_view&confID=65&abstractID=30412
7. Nosov V., et al. Validation of serum biomarkers for detection in early-stage ovarian cancer.
American Journal of Obstetrics and Gynecology. June 2009: 200(6): 639.e1-639.e5.
