Ovarian cancer screening yields undue false positives

January 13, 2006

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

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

Transvaginal ultrasound (TVU) and CA 125 have been given serious-candidate status for cancer screening in this setting. Yet neither has shown results convincing enough to secure screening status.

"Results from the initial year of screening show that TVU and CA 125 cannot currently be recommended for widespread use in the general population," said principal investigator Dr. Saundra S. Buys, a professor of oncology at the University of Utah's School of Medicine.

The NCI study relates to the ovarian cancer section of the institute's Prostate, Lung, Colorectal, and Ovarian (PLCO) 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 have randomized 39,115 women to date, 28,816 of whom have undergone 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 in both (Am J Obstet Gynecol 2005;193[5]:1630-1639).

Women who had suspicious results in one or both screening tests underwent other diagnostic procedures to confirm or rule out cancer. From 570 women who have undergone surgery, investigators have detected 29 neoplasms (26 ovarian, two fallopian, and one primary peritoneal), 20 of which were invasive. The remaining 541 women, however, did not have cancer.

Researchers determined the positive predictive values for invasive cancer for abnormal CA 125, TVU, or both tests were 3.7%, 1.0%, and 23.5%, respectively.

"Future results from the additional PLCO screenings and subsequent follow-up will be needed before a final assessment of this screening strategy can be made," Buys said.

Enrollment for the ovarian cancer screening part of the PLCO trial began in 1993. Baseline screening for those enrolled included CA 125 and TVU. Women also received additional annual screening and follow-up. Enrollment ended in 2001.

"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, Sc.D.

Researchers expect to find additional biological markers for early detection of ovarian cancer.

For more information from the Diagnostic Imaging archives:

Genetic findings affect diagnosis, treatment of ovarian cancer

Enhanced ultrasound reveals gynecological disorders

Task force says no to routine genetic testing