Trial Finds Ovarian Cancer Screening Method is Ineffective in Reducing Deaths

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August 12, 2011

Ovarian cancer is the fifth most common cause of cancer death in women. Survival rates improve dramatically with early detection and treatment. Unfortunately, there is currently no good method to detect this disease in the early stages. Most cases are discovered during routine examinations and are often in the late stages when no treatment is effective. An article published in the June 4th issue of the Journal of the American Medical Association reported a study to determine if annual screening with two different tests, a blood and an ultrasound test, could identify ovarian cancer in the early stages and help reduce mortality from this disease. The authors found that in average-risk women, annual screening with the dual tests was no better than routine medical care in reducing the number of deaths due to ovarian cancer.

The results are from the ovarian cancer component of the Prostate, Lung, Colorectal, and Ovarian (PLCO) Cancer Screening Trial. The PLCO is a large, randomized, controlled trial that is part of ongoing research to improve cancer outcomes through early detection. Early-stage ovarian cancer confined to the ovary (stage I) has a five-year survival of 92%, but symptoms may be non-specific or absent, and most women are not diagnosed until the disease has progressed. The five-year survival for patients who are diagnosed at an advanced stage drops to 30%.

The ovarian cancer component of the PLCO trial tested the effect of two screening techniques on ovarian cancer mortality, cancer antigen-125 (CA-125) and transvaginal ultrasound. CA-125 is a laboratory test that screens for elevated levels of the CA-125 protein in the blood. CA-125 is a protein found on the surface of most ovarian cancer cells, but it is not specific to cancer cells and is sometimes associated with healthy cells. Transvaginal ultrasound, a radiologic imaging test, is used to detect abnormal ovarian shape and volume.

The PLCO trial included 78,216 women from the general population, ages 55 to 74, with no known risk factors such as family history of ovarian cancer, who were recruited at 10 screening centers across the U.S. Roughly half the women were placed in the screening group and were offered annual CA-125 testing for 6 years and transvaginal ultrasound for 4 years, while the other half, the control group, received only their usual medical care and no additional screening. Participants were followed for an average of 12.4 years.

At the end of the trial, there were 118 deaths in the group that received CA-125 and transvaginal ultrasound screening and 100 deaths in the control group that received usual medical care. While ovarian cancer mortality was slightly higher in the group that received screening, the difference between the groups was not statistically significant.

Additionally, there were 3,285 women with false positive diagnoses as a result of the dual screening. Of the 1,080 women from that group who had surgical interventions, 163 (15%) experienced at least one major complication.

The researchers concluded that yearly screening with CA-125 and transvaginal ultrasound did not reduce deaths from ovarian cancer in average-risk women while increasing their exposure to invasive procedures and complications from false positive results. Based on statistical considerations, the authors suggested that even optimized annual screening may not detect cancers early enough to reduce mortality because aggressive cancers progress through initial stages rapidly and elude early detection.

Though results from this large study are disappointing and currently do not offer improved screening options for women, research is ongoing. Scientists continue to study testing methods that would find ovarian cancer in the early, most treatable stages, ultimately improving survival rates.

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NOTE: This article is based on research that utilizes the sources cited here as well as the collective experience of the Lab Tests Online Editorial Review Board. This article is periodically reviewed by the Editorial Board and may be updated as a result of the review. Any new sources cited will be added to the list and distinguished from the original sources used.

Buys SS, et al. Effect of screening on ovarian cancer mortality in the Prostate, Lung, Colorectal, and Ovarian (PLCO) Cancer Randomized Screening Trial. ASCO 2011; Abstract 5001.

Buys SS et al. Effect of screening on ovarian cancer mortality. The Prostate, Lung, Colorectal, and Ovarian (PLCO) cancer screening randomized trial. JAMA 2011; DOI: 10.1001/jama.2011.766. Available online at http://jama.ama-assn.org/content/305/22/2295.full through http://jama.ama-assn.org. Accessed July 2011. 

ASCO: Screening Fails to Lower Ovarian Cancer Mortality. By Charles Bankhead, Staff Writer, MedPage Today. Published: June 04, 2011. Available online through http://www.medpagetoday.com. Accessed July 2011.

Andrew M. Kaunitz, MD. Ovarian Cancer Screening: No Advantage. Journal Watch Women's Health, June 16, 2011. Available online at http://womens-health.jwatch.org/cgi/content/full/2011/616/1?q=etoc_jwgenmed through http://womens-health.jwatch.org. Accessed July 2011.