False positives foil hopes for ovarian cancer screening

April 2, 2006

Transvaginal ultrasound and serum CA 125 blood tests, used individually or in combination, can detect ovarian cancer early, according to preliminary results from a study conducted by the National Cancer Institute. But both tests produce too many false positives, prompting needless surgeries.

Transvaginal ultrasound and serum CA 125 blood tests, used individually or in combination, can detect ovarian cancer early, according to preliminary results from a study conducted by the National Cancer Institute. But both tests produce too many false positives, prompting needless surgeries.

While each technique has been considered for ovarian cancer screening, neither has shown results convincing enough to secure that status, according to Dr. Saundra S. Buys, a professor of oncology at the University of Utah's School of Medicine in Salt Lake City.

"Results from the initial year of screening show that TVU and CA 125 cannot be recommended for widespread use in the general population," Buys said.

The study is one component of the NCI's Prostate, Lung, Colorectal, and Ovarian cancer screening trial. It seeks to establish if screening with either technique can reduce ovarian cancer mortality in middle-aged and elderly women.

Buys and colleagues randomized nearly 40,000 women, 28,816 of whom underwent baseline screening. They found abnormal TVU results in 1338 women (4.7%) and abnormal CA 125 in 402 (1.4%). Thirty-four women (0.1%) had abnormal results on both tests (Am J Obstet Gynecol 2005;193(5):1630-1639).

Women with suspicious results in one or both tests underwent other diagnostic procedures to confirm or rule out cancer. Out of 570 women who underwent surgery, investigators detected 29 neoplasms (26 ovarian, two fallopian, and one primary peritoneal), 20 of which were invasive. The positive predictive values for invasive cancer for abnormal CA 125, TVU, or both tests were 3.7%, 1%, and 23.5%, respectively.

"As women are followed for a longer period of time, it will be possible to examine how screening tests behave in special groups of women, for example, those with breast or ovarian cancer in their families," said coauthor Patricia Hartge.