Ovarian cancer, the most lethal gynecological cancer known as the "silent killer" because it usually grows undetected until it's too widespread to treat, may not be so invisible after all. Two controversial, early screening techniques may pick up the tumors better than critics previously believed.

A randomized controlled trial of more than 202,000 postmenopausal women found that a blood test to measure a tumor marker called CA-125, followed by a vaginal ultrasound, detected 48 percent of cancers in their early stages, according to a study set to be published in next month’s The Lancet Oncology. Some 90 percent of ovarian cancers are curable when they're caught early, but right now, only a quarter of women are diagnosed at that stage.

"That is the potentially encouraging finding," says Martee Hensley, an associate attending physician in the gynecologic medical oncology service at Memorial Sloan-Kettering Cancer Center in New York, who was not involved in the study. Late-stage ovarian tumors are curable only a third of the time, yet they make up the majority of diagnoses. "If we could shift that so that half or three-quarters are found at early-stage disease," Henseley says, "we think that should translate into better survival rates."

Some patient advocates have pushed the CA-125 blood test and trans-vaginal ultrasound, but some doctors believed that they weren’t sensitive enough (meaning they'd miss early-stage cancers) or specific (meaning that they'd detect things that would turn out not to be cancer). "These data may argue to the contrary," Hensley says.

The study doesn’t prove that women whose cancers are detected early using the methods live longer than those whose aren’t. But the women in the trial, who live in England, Wales and Northern Ireland, will be followed through 2014 to track whether the tests cut the ovarian cancer death rate.

An estimated 21,650 cases of ovarian cancer were diagnosed in the U.S. last year, and 15,520 women died from the disease, according to the National Cancer Institute (NCI). Women who aren’t carriers of the BRCA1 or BRCA2 genetic mutations that raise the risk of breast and ovarian cancers, and who don’t have a mother or sister with ovarian tumors, aren’t advised to undergo CA-125 and trans-vaginal ultrasound testing, which – at least until now – haven’t been thought to be reliable for healthy women, who naturally produce some amount of CA-125 protein even if they don't have ovarian tumors. An ongoing clinical trial at the NCI is evaluating CA-125 screens for high-risk women who are BRCA carriers and have family histories of ovarian cancer.

Image of female reproductive tract © iStockphoto/Sebastian Kaulitzki