Experts say that although the test has tremendous potential, it is still years from widespread use. But if proven effective with more testing, it would fill a significant void.

Currently, there are no tests that can reliably detect either ovarian or endometrial cancer, which affects the uterine lining. Research teams have been trying for several years to find a screening test that could identify these cancers early, when there is a better chance of a cure.

"Pap smears have had a tremendous impact in reducing the rate of cervical cancer in the United States," said Dr. Andrea Myers of Dana-Farber Cancer Institute, a co-author of the commentary on the study published in Science Translational Medicine.

"The lack of an equally effective screening test for women at high risk for endometrial or ovarian cancer has created a great deal of interest in developing tests that could identify these cancers by their genetic ‘signature' - the collection of specific mutations within them," she said.

"This new study is an important step in that direction."

The new approach, developed by a team at Johns Hopkins Kimmel Cancer Center in Baltimore, piggybacks on routine Papanicolaou or Pap testing, which is already done routinely to detect cervical cancer.

The idea is to take fluid collected from the cervix for Pap tests and use gene sequencing technology to look for genetic changes that would only be found in endometrial and ovarian tumors.

Since Pap tests occasionally contain cells shed from the ovaries or the lining of the uterus, cancer cells from these organs could be present in the fluid as well.

The team tested for mutations in 24 endometrial and 22 ovarian cancers.

'EXCITING FIRST STEP'

"We could detect 100 percent of endometrial cancers and 40 percent of ovarian cancers, even at the earliest stages of their disease, and we can do it without any false positives," said Dr. Luis Diaz, associate professor of oncology at Johns Hopkins, who worked on the study published on Wednesday in Science Translational Medicine.

Diaz called the study "an exciting first step."

"We're seeing high sensitivity in endometrial cancer. We're seeing moderate sensitivity in ovarian cancer, and we're seeing no false positives," he said.

That offered enough rationale to start tests on 100 ovarian cancers of different stages and 100 endometrial cancers, as well as a large number of samples from healthy women.

The team hopes to complete that testing by the end of the year.

Dr. Shannon Westin, an expert in gynecologic cancers at the University of Texas MD Anderson Cancer Center, said the need for a screening test for these two cancers is great.

In the United States, the two cancers combined are diagnosed in 70,000 women each year, and about 23,500 women will die from these cancers.

Westin, who co-wrote a commentary on the study, said the paper is "very compelling and very interesting" that you could find evidence of these cancers in a screening test using fluid from Pap tests.

But the test must still be validated and shown to be effective in a large populations of women, a process that could take 10 to 15 years.

"It's a great first step. It is a proof of principle that this can be done. Patients are used to getting the Pap smear. They understand it," she said. That might mean women would ultimately be comfortable getting this type of test.

Dr. David Chelmow, a professor of obstetrics and gynecology at Virginia Commonwealth University Medical Center, who was not involved with the research, said it would be "fantastic" to have a test that would reliably detect cancers.

"It's an innovative idea. It's neat. But the question is really going to be what happens when this gets more thoroughly tested," he said.

Diaz said currently there are no tests to screen for these cancers early. The experimental test would cost about $100, but with the falling cost of sequencing technology, he estimates it will be half or even a tenth of that cost within the next year.

(Reporting by Julie Steenhuysen; Editing by Jilian Mincer and Eric Walsh)

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