Ovarian Cancer Screening Methods Inaccurate
False-positive results cause too many women to undergo unnecessary surgeries, study finds
MONDAY, Nov. 7, 2005 (HealthDay News) -- Two methods used to screen women for suspected ovarian cancer may identify too many false-positive test results to be useful, researchers conclude.
The tests -- transvaginal ultrasound (TVU) and a screen for a protein biomarker called CA-125 -- can be used alone or together and do find cancers, a new study shows. But they also falsely identify too many 'cancers' where malignancy is not present. These false-positive results often lead to unnecessary surgeries, the researchers report in the Nov. 15 issue of the American Journal of Obstetrics and Gynecology.
Ovarian cancer is the seventh-leading cancer diagnosed in women, but because it is usually diagnosed so late it remains one of the most deadly, according to the American Cancer Society. Over 22,000 U.S. women are diagnosed with the disease each year, and more than 16,000 die from ovarian malignancies annually. Because accurate detection is key to saving lives, researchers have long sought a reliable test to identify tumors early on.
"The goal [of this study] was to determine whether screening for ovarian cancer could detect ovarian cancer at an early enough stage to increase the likelihood of cure," said lead author Dr. Saundra S. Buys, the co-director of the Family Cancer Assessment Clinic at the Huntsman Cancer Institute in Salt Lake City, Utah. "So far, it's too early yet to draw those conclusions, because we need more follow-up," she added.
The long-term goal of the trial is to see if screening with TVU and/or CA-125 decreases ovarian cancer mortality in women ages 55 to 74, Buys noted.
In the study, called the Prostate, Lung, Colorectal and Ovarian (PLCO) Cancer Screening Trial, Buys' team collected data on nearly 29,000 healthy women screened with TVU and/or a CA-125 blood test. Among these women, 1,338 had an abnormal TVU and 402 had an abnormal CA-125 blood test. In addition, 34 women received abnormal results on both tests.
Despite the high number of abnormal test results, Buys' group found just 29 tumors, of which 20 were invasive cancers, the researchers report. In all, 570 women underwent a surgical procedure, but 541 did not end up having cancer.
Given these results, "it does not appear that screening for ovarian cancer the way it was done in this trial is something that should be applied to the general population," Buys said.
"The biggest problem is if a lot of women go out and get these tests, there will be many more women who are going to get surgery who don't have ovarian cancer," Buys said. "And some of those surgeries have complications."
Buys noted that the same high incidence of false-positives is also seen when these tests are used to screen for prostate and lung cancer.
She recommended that instead of having these screenings, women should pay attention to their overall health. "If they have any abdominal symptoms, they should go to their doctor and get them fully evaluated," she said.
"It may be appropriate to screen for ovarian cancer in women who have abdominal symptoms, but for women who have no medical symptoms, doing screening for ovarian cancer results in a lot of false-positives," Buys said.
In addition, Buys advises women to keep their weight at a healthy level and to get plenty of exercise. "And pay attention to any new symptoms or problems that develop," she said.
One expert believes that in time a better screening test will be found.
"Screening for ovarian cancer is difficult, and unfortunately, several trials utilizing CA-125 markers and transvaginal ultrasounds have suggested that these methods are both inadequately sensitive and inadequately specific for widespread utilization in the general population," said Dr. Robert Morgan, Jr., the section head of medical gynecologic oncology at City of Hope Cancer Center, Duarte, Calif.
This study showed that many women underwent invasive surgical procedures and were found to have benign conditions, while only a few women with invasive ovarian cancer were detected with early, more curable disease, Morgan noted.
"All, however, is not bleak," Morgan said. "For many years it was thought that early-stage ovarian cancer did not give symptoms. Several papers published in the past four to five years, however, have shown that 90 percent of women with early-stage ovarian cancer do have symptoms."
The problem is that the symptoms are usually non-specific abdominal or urinary symptoms or discomfort during sexual activity, Morgan said. "However, persistent non-specific symptoms that occur in women, usually for only a few months, in patients who previously didn't have any symptoms, require more investigation by their physicians," he said.
Morgan added that more is being done to detect bloodstream markers, which will make screening more specific and more sensitive. "I am sure that with more research, early screening for ovarian cancer will become a reality, and we will be able to treat increasing numbers of patients for cure of this difficult disease," he said.
Learn more about ovarian cancer at the American Cancer Society.