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New Pap test may screen for three cancers instead of one

A new study suggests that the traditional Pap smear may be tweaked to detect three cancers instead of one.

The study was small, and the test is far from ready for clinical use, but researchers are hopeful that the method may one day have a major impact on the way women are screened for cancer.

“Is this the harbinger of things to come? I would answer yes,” author Dr. Bert Vogelstein tells the New York Times.

One of the things that makes the new screening method so promising is that it doesn’t require an additional test — women are already getting regular Pap smears.

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During a regular Pap test, cells from the cervix are collected and then examined under a microscope for abnormalities that indicate cervical cancer. In recent years, it has become possible to use DNA testing on these samples to screen for the human Papillomavirus (HPV), which causes cervical cancer.

This new study, published Wednesday in the journal Science Translational Medicine, found that DNA testing of these same samples could also be used to screen for cancers of the uterus and ovaries.

For the study, scientists identified genetic mutations present of ovarian and uterine cancers. They then used DNA testing methods on 46 Pap smears from women known to have cancer. The test identified at least one genetic mutation in all 24 samples taken from women with uterine cancer, and in nine of the 22 samples taken from women with ovarian cancer.

This would seem to indicate that the method will be far more useful and effective in screening for uterine cancer, and yet researchers say that the test may have a bigger impact on diagnosing ovarian cancer, because ovarian cancer lacks obvious symptoms and reliable screening tests, and is therefore often deadly.

Study co-author Luis Diaz Jr. tells the New York Times that the ovarian cancer test may have been less effective because cells from the ovaries must travel down the fallopian tubes and through the uterus to arrive at the cervix where the sample is extracted. Diaz suggests that a different sampling brush that actually penetrates the cervix might collect a better sampling of those cells.

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The next step will be to reproduce results indicating the test’s efficacy in hundreds of women both with and without cancer. Diaz estimates the test would add about $75 to the current cost of a Pap smear.

This study comes less that a year after the American College of Obstetricians and Gynecologists altered their guidelines concerning Pap smears, changing the recommended frequency from "at least every three years" to "no more than once every three years." This reduction was made in the face of research which found that over-testing was leading to false positives and unneccesary procedures.

In Canada, the guidelines still recommend that women 21 and over should be tested once per year until they have had two normal test results in a row, and then only once every three years. These guidelines are currently under review.

Whether or not the Pap's newfound potential to screen for multiple cancers will affect these guidelines remains to be seen.