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Clinical Trial Results

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  • Posted: 07/27/2011

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Ovarian Cancer Screening Method Fails to Reduce Deaths from the Disease

New results from the NCI-sponsored Prostate, Lung, Colorectal and Ovarian (PLCO) Cancer Screening Trial show that screening for ovarian cancer with transvaginal ultrasound (TVU) and the CA-125 blood test did not result in fewer deaths from the disease compared with usual care. In addition, false-positive results from the two screening methods often led to unnecessary surgeries and other serious complications. The results were presented June 4 at the 2011 American Society of Clinical Oncology (ASCO) annual meeting and appeared online June 8, 2011, in JAMA.

The PLCO trial is a randomized controlled trial of adults 55 to 74 years of age. The 78,216 women who enrolled were assigned to undergo either annual screening with TVU and CA-125 testing or to receive usual care. (Most women in the usual care group underwent bimanual examination with ovarian palpation.) Participants were screened at 10 centers across the United States between November 1993 and July 2001 and were followed for up to 13 years. There were 118 deaths from ovarian cancer in the screened group compared with 100 deaths in the usual-care cohort.

The false-positive rate in the PLCO trial was approximately 5 percent of those screened during each round of screening. Of the 3,285 women with false-positive results in the study, 1,080 underwent surgical follow-up. Among those, 163 women (15 percent) experienced at least one serious complication. A 2009 report from the PLCO study found that many of the positive screening results from TVU and CA-125 turned out not to be cancer. The researchers estimated that only 1.6 out of every 100 women who test positive for signs of ovarian cancer with these tests actually have cancer.

With these results, and the efficacy of these tests being ruled out, investigators will explore other screening options, the study authors noted. Some evidence suggests that ovarian tumors need to be found when they are relatively small—considerably smaller than the current threshold used for TVU, explained Christine Berg, M.D., of NCI’s Division of Cancer Prevention. “Had the trial tested a lower CA-125 threshold, it may have been possible to detect cancers at an earlier stage,” said Dr. Berg. “However, this would be at the expense of more false-positive results and perhaps overdiagnosis of benign tumors.”

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