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    Cell free DNA and oncology

     


     

    Dr. Levine is Clinical Fellow, Reproductive Endocrinology & Infertility, Ronald O. Perelman and Claudia Cohen Center for Reproductive Medicine, Weill Cornell Medical College, New York.

     

     

    Dr. Goldschlag is Assistant Professor of Clinical Obstetrics and Gynecology and Assistant Professor of Clinical Reproductive Medicine, Ronald O. Perelman and Claudia Cohen Center for Reproductive Medicine, Weill Cornell Medical College, New York.

     

     

    In September’s installment of Tech Tools, Noninvasive prenatal testing: A new standard of care? we discussed the utility of cell-free fetal DNA in prenatal diagnosis and the capabilities of the 4 commercially available noninvasive prenatal testing technologies. In this continuation of our cell-free DNA series, we discuss the role of cell-free nucleic acids as noninvasive biomarkers in oncology.

    Colorectal screening

    In August 2014, the FDA approved Cologuard, the first stool-based colorectal screening test. Cologuard assesses the presence of colorectal neoplasia-associated DNA markers and occult hemoglobin in stool.1 The test takes advantage of the fact that the gastrointestinal tract is constantly regenerating and shedding epithelial cells. As these cells are sloughed, they release their DNA and are removed through the stool stream, making them an ideal noninvasive target.2

    A recently published study found that the multi-target stool DNA testing (targeting methylation and mutation biomarkers that are associated with cancer and precancer) detected significantly more cancers than the American College of Gastroenterology-recommended fecal immunochemical test (FIT), although there were more false-positive results (Cologuard detected 86.6% true negatives for a false-positive rate of 13.4%, whereas FIT detected 94.9% of true-negative patients, for a false-positive rate of 5.1%).3 While many may be concerned about this relatively high risk of false-positives, others may argue that it is more desirable for a screening test to catch as many affected cases as possible (ie, to have high sensitivity) even if it means that some unaffected individuals may be misclassified as at-risk (lower specificity).

    The US Preventive Services Task Force (USPSTF) recommends screening for colorectal cancer using fecal occult blood testing, sigmoidoscopy, or colonoscopy in adults, beginning at age 50 and continuing until age 75.4 According to the Centers for Disease Control and Prevention (CDC), if everyone age 50 years or older had regular screening tests as recommended, at least 60% of colorectal cancer deaths could be avoided.1 However, barriers to adherence with these screening recommendations include lack of access to a provider, the cumbersome nature of the sigmoidoscopy/colonoscopy’s required bowel prep, and incomplete adherence to the pretest dietary restrictions. Cologuard eliminates all those barriers: it only requires the patient to collect a stool sample at home and mail it to the Exact Sciences laboratory.

     

    Brian A. Levine, MD, MS, FACOG
    Dr. Levine is Practice Director at the Colorado Center for Reproductive Medicine, New York, New York.
    Dan Goldschlag, MD, FACOG
    Dr. Goldschlag is an assistant professor of Clinical Obstetrics and Gynecology and Assistant Professor of Clinical Reproductive Medicine ...

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