March 20 (HealthDay News) -- A screening regimen that combines ultrasound and a blood test to detect CA125, a marker for ovarian cancer, fails to discover the cancer in its early stages and often results in unnecessary surgery, a new study shows.
This finding contrasts with another recent study that found that these same two tests did find early cancer. Taken together, experts say these studies highlight the need to find an effective screening method for this deadly cancer, which is often called the "silent killer."
"The jury is still out on the efficacy of screening with CA125 and transvaginal ultrasound in terms of reducing the mortality rate of ovarian cancer," said lead researcher Dr. Edward Partridge, director of the University of Alabama Birmingham Comprehensive Cancer Center.
"In this study, we do not have mortality data on the screening versus the non-screening group, so no conclusions can be made of the impact of screening with CA125 and transvaginal ultrasound," he added.
This study only reports data on women who were screened, Partridge noted. "We learned that the positive predictive value for the combination of tests is pretty low -- in the 1 to 1.3 percent range," he said. "A substantial number of the tests are false positives."
In addition, screening with transvaginal ultrasound lead to a higher rate of surgery for positive findings than positive CA125, Partridge said. "Transvaginal ultrasound leads to more 'unnecessary' surgeries," he said.
And a high percentage of the cancers detected through screening were late-stage malignancies, Partridge said. "If you detect them at a late stage, it is unlikely that you are going to impact mortality," he said. "In order to affect mortality, one has to detect them at an earlier stage."
The report is published in the April issue of Obstetrics & Gynecology.
For the study, Partridge's team collected data on 34,261 women who underwent annual screening for CA125 and also had transvaginal ultrasound.
The researchers found that over the four years of screening, transvaginal ultrasound produced more positive findings for cancer than CA125 screening. In fact, CA125 positive tests decreased from 60 percent in the first year to 34 percent in the third year.
Of the 89 invasive ovarian cancers diagnosed, 60 were detected through screening. In addition, 72 percent of the screen-detected cancer were late-stage cancers, the researchers reported.
Partridge noted that even detecting cancer early may not have an impact on mortality. "In any screening trial, the ultimate test of its usefulness is does it impact mortality," he said.
Based on the findings of this study and the study published in the March 10 online edition of The Lancet Oncology, this screening method will not have any effect on mortality, Partridge said. "What we need is a more sensitive and specific screening test," he said.
In that study, a British research team found that screening was able to identify most women with cancer. The combination of the blood test and ultrasound found 90 percent of the cancers, while ultrasound alone found 75 percent of the cancers.
Almost 50 percent of all the cancers found were in an early stage (stage I or II), the researchers noted. And 48 percent of the more invasive ovarian cancers detected were designated as being stage I tumors. Usually, only 28 percent of ovarian cancers are identified in this early stage, the researchers pointed out.
Dr. David G. Mutch, the Ira C. and Judith Gall Professor of Obstetrics and Gynecology at Washington University, St. Louis, and author of an accompanying journal editorial, agreed there is no worthwhile screening test for ovarian cancer as yet.
"Patients who were screened presented at the same stage as they would have if they were unscreened," Mutch said. "There is no good screening test at this point."
Mutch added that there is no reason to screen for ovarian cancer in the general population at this point. "The prevalence of the diseases is so low, one in 2,500, and the specificity of the tests are so low, that we are going to operate on a lot of patients unnecessarily," he said.
SOURCES: Edward Partridge, M.D., director, University of Alabama Birmingham Comprehensive Cancer Center; David G. Mutch, M.D., Ira C. and Judith Gall Professor of Obstetrics and Gynecology, Washington University, St. Louis; April 2009, Obstetrics & Gynecology