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Large trial finds annual screening doesn’t reduce deaths from ovarian cancer

Annual screening for ovarian cancer with the CA-125 blood test and transvaginal ultrasound (TVUS) does not reduce a woman’s risk of dying from the disease, according to the results of a large clinical trial sponsored by the National Cancer Institute. Ovarian cancer is 90% curable when treated early, but most cases are diagnosed late, when the five-year survival rate is less than 30%. Nearly 14,000 women die from the disease every year.

As part of the Prostate, Lung, Colorectal, and Ovarian Cancer Screening Trial, researchers at the University of Utah evaluated whether yearly screening could lead to earlier detection and reduce mortality. Results were presented at the American Society of Clinical Oncology meeting in Chicago and published online in The Journal of the American Medical Association on June 4, 2011.

The study. Investigators at 10 centers across the United States enrolled 78,216 women ages 55 to 74 who were at average risk for ovarian cancer and followed them for up to 13 years. Participants were assigned at random to either annual screening or usual medical care without screening. Women in the screening group were offered an annual CA-125 blood test (a nonspecific test for ovarian cancer) for up to six years, and TVUS annually for up to four years. The women and their physicians were informed of any suspicious abnormalities found during screening; the physicians were responsible for managing any further diagnosis and therapy.

The results. In the screening group, there were 212 cases of ovarian cancer and 118 deaths from the disease. In the usual care group, there were 176 cases of ovarian cancer and 100 related deaths. When the researchers took into account the total number of participants and factored in the total surveillance time — that is, when they calculated mortality per “10,000 person-years” — they found that the death rate was slightly higher in the screening group, but the difference wasn’t statistically significant, meaning that it might have been due to chance. Screening not only failed to improve the survival rate but also led to unnecessary invasive procedures. In the screening group, there were false-positive results in 3,285 women, of whom 1,080 underwent surgery as part of their diagnostic workup. Of those who underwent surgery, 15% had at least one major complication as a result.

Limitations and implications. Although this large-scale trial found that screening women at average risk for ovarian cancer with CA-125 and TVUS did not decrease their risk of death from the disease, the results don’t necessarily mean that these tests are useless. The researchers suggest that the thresholds for abnormal results that were used in this study may not have been low enough to catch cancers at their earliest stages. Also, studies suggest that ovarian cancer often advances quickly in the early stages, so yearly screening may be insufficient. Monitoring changes in CA-125 levels more frequently might lead to more accurate diagnoses.

Another clinical trial is expected to provide additional insight into the potential of screening with CA-125 and TVUS. The U.K. Collaborative Trial of Ovarian Cancer Screening is following more than 200,000 women randomly assigned to usual care, annual TVUS, or annual CA-125 testing followed by TVUS if indicated by the blood test results. Preliminary data from this study suggest that both screening methods are more effective at detecting early ovarian cancer than usual care. However, final results won’t be known until 2015.

Posted by: Dr.Health

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