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Potential breakthrough in ovarian cancer screening

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Micrograph of a low malignant potential mucinous ovarian tumour.

Clinical trial data published recently in the medical journal Cancer has indicated that mass screening for ovarian cancer may be possible.

Historically, ovarian cancer has been  difficult to diagnose in its early stages, as its symptoms (e.g., pelvic and abdominal pain or persistent bloating) are often very subtle and attributed to other common ailments.  Moreover, early-stage tumors in the ovaries are very hard to detect, and are often discovered only after the cancer spreads and advances to later stages, when it is too late to be treated effectively (ovarian cancer has a survival rate of up to 90% when diagnosed early, and less than 30% when discovered in its later stages).

A traditional biomarker for ovarian cancer is a blood protein called CA-125, higher levels of which can indicate the presence of ovarian cancer.  Unfortunately, testing for elevated CA-125 levels is not alone sufficiently reliable for mass ovarian cancer screening, as the test can fail to detect cancer in many cases while also producing false positives. Confirming an initial diagnosis based on CA-125 levels has generally required surgery to inspect the abdominal cavity, biopsies (tissue samples for microscopic analysis) and searching for cancer cells in the abdominal fluid.

New testing methods, including that used in the aforementioned clinical trial, employ CA-125 blood tests for initial screening method to sort patients into risk groups. Patients classified as low- and medium-risk are retested for elevated CA-125 levels after a year and three months, respectively. High-risk patients undergo an transvaginal ultrasound scan to hunt for tumors.

In the aforementioned clinical trial, ten women received surgery based on their ultrasound scans and all of the cancers detected were found at an early stage. This clinical trial of 4,051 women was conducted in the United States at the University of Texas, and provides encouraging results as the world awaits the outcome of a larger and more definitive study of 50,000 women in the United Kingdom, scheduled for completion in 2015.

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