WASHINGTON--Only a screening test that can reliably find stage
I tumors will have any real impact on overall ovarian cancer mortality,
and transvaginal ultrasound does not appear to fulfill that requirement.
Although the technique can detect stage I ovarian cancers, its
specificity is not high enough to make it useful as a general
screening test, Beth Y. Karlan, MD, said at the American Cancer
Society National Conference on Gynecological Cancers.
Dr. Karlan said that proven screening tests such as Pap smears
and mammography work because the biology of the tumors is well
understood, and the tumor sites are more accessible than the ovaries.
With ovarian cancer, the molecular events leading up to the development
of the cancer are not well known, nor is the history of any precursor
disease. However, studies of p53 mutations indicate that the disease
begins with a single cell that then proliferates and metastasizes.
A monoclonal origin for ovarian carcinomas would theoretically
point the way to detection of early neoplastic changes in the
ovary. "We know how it starts, but we still don't know how
long it takes to get from stage I to stage III," said Dr.
Karlan, of the department of obstetrics and gynecology, Cedars-Sinai
Medical Center, Los Angeles.
"We need to better understand early tumor biology in terms
of what allows these cells to transform and proliferate, in order
to find a good screening test that would diagnose early-stage
disease," she added.
Two Screening Studies
Dr. Karlan reported on a University of Kentucky trial of 3,220
asymptomatic postmenopausal women given annual transvaginal ultrasound
screens for 5 years to find early alterations in the ovary. Forty-four
women had positive transvaginal ultrasound scans; three proved
to be malignant tumors (two were stage I), and 41 were benign.