Ovarian Cancer Screening Using Ultrasound and CA125 Finds both Early and Late Stage Cancers, But Also Many False Positives A new study from the National Cancer Institute (NCI), part of the National
Institutes of Health, shows that currently available screening methods such as
transvaginal ultrasound (TVU) and testing for a protein biomarker called
CA-125, alone or in combination, can detect ovarian cancer but can also produce
many false-positive test results, causing needless surgery. This report, which
summarizes preliminary results from the Prostate, Lung, Colorectal and Ovarian
(PLCO) Cancer Screening Trial, appears in the November 15, 2005, American
Journal of Obstetrics and Gynecology*.
These findings, the first published ovarian cancer screening results from NCI's
ongoing multicenter PLCO Cancer Screening Trial, are based on an analysis of
the trial participants' initial screening tests. CA-125 and TVU have been
considered as potential screening techniques, although studies to date have not
shown that they can be effective and thus they are not currently recommended.
The long-term objective of the PLCO Trial is to determine whether screening
with TVU and/or CA-125 decreases ovarian cancer mortality in women ages 55 to
74.
Of the 28,816 healthy women who underwent the initial (baseline) screening,
1338 (4.7 percent) had an abnormal TVU and 402 (1.4 percent) had an abnormal
CA-125 blood test. Thirty-four women (0.1 percent) had abnormal results in both
screening tests. Among the women with abnormal test results, 29 tumors were
detected, 20 of which were invasive cancers.
Women who had an abnormal test result in one or both screening tests underwent
a variety of diagnostic procedures to determine whether cancer was present,
including 570 women who underwent a surgical procedure as follow-up. Thus, 541
women underwent surgery but did not have cancer.
"Ovarian cancer is a disease that is often fatal, and both patients and
physicians are anxious to find ways to detect it at an earlier, more curable
stage," said first author on the study, Saundra Buys, M.D., University of Utah,
Salt Lake City. "However, the results from the initial year of screening show
that TVU and CA-125 cannot currently be recommended for widespread use in the
general population. 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."
Enrollment in the PLCO study began in 1993 and ended in 2001. When they
initially enrolled in the study, women in the intervention arm underwent
baseline ovarian cancer screening with CA-125 and TVU and received additional
annual screenings and follow-up. Women in the control arm of the study were not
screened but were observed over time.
The results published in this report reflect analysis of the initial baseline
screenings for women enrolled between 1993 and 2001. The results of subsequent
years screening with TVU and CA-125 are not yet available, and it is these
additional results that will ultimately determine whether this screening
strategy is effective in reducing mortality from ovarian cancer. These results
will not be available for several years.
At the time of the baseline examination, both TVU and CA-125 had low predictive
values -- a measure of how likely a person with a positive test result is to
have the disease of interest -- when used to screen healthy women for ovarian
cancer. Many investigators feel that an acceptable predictive value for an
ovarian cancer screening test is around 10 percent. The predictive values of
these screening tests were 3.7 percent for an abnormal CA-125 test, 1 percent
for an abnormal TVU, and 23.5 percent if both tests were abnormal. Although
having an abnormality in both tests had a fairly high predictive value, only 9
of the 29 tumors (31 percent) were associated with abnormalities in both tests.
Patricia Hartge, Sc.D., a NCI investigator on the PLCO project, added, "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 family." Investigators will also be able to
study whether other biological markers which are proposed but unconfirmed are
useful for early detection of ovarian cancer.
The PLCO is currently scheduled to collect data until 2008.
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For more information about cancer, visit the NCI Web site at
http://www.cancer.gov or call NCI's Cancer Information Service at 1-800-4
CANCER (1-800-422-6237).
*Buys SS, Partridge E, et al. "Ovarian Cancer Screening in the Prostate, Lung,
Colorectal and Ovarian (PLCO) Cancer Screening Trial: Findings from the Initial
Screen of a Randomized Trial." American Journal of Obstetrics and Gynecology,
November 15, 2005.
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