Maternal Malignancy and Noninvasive Prenatal Testing

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Diana W Bianci I am Executive Director of the Mother-Infant Research Institute at Tufts Medical Center in Boston, and I'm a reproductive geneticist So I have both a research and clinical practice in prenatal diagnosis We did this study because non-invasive prenatal testing using sequencing of cell-free DNA in the mother's plasma is the fastest growing area of prenatal testing and, indeed, of genomic medicine

As the volume of tests has expanded, we become increasingly aware of the so-called false positive cases By that, I mean that approximately 02% of the time, there is a discrepancy between the results of the prenatal test, in which in aneuploidy is reported in the result from the diagnostic pedal procedure, the amniocentesis, or the chorionic villus sampling So were interested in a situation where the fetal chromosomes are normal, but the prenatal test shows that there's aneuploidy detected So were interested in the possible explanations for that discrepancy

In this particular study we used a database from The Illumina Clinical Laboratory in California consisting of over 125,000 prenatal DNA test reports, and of that group, 3757 reported aneuploidy detected in the pregnant woman, approximately 3% of tests The normal clinical protocol is to recommend a diagnostic procedure to fully evaluate the fetal chromosomes status In this study, we looked at women who had an abnormal prenatal screening report, plus a normal fetal chromosome report, or a normal, healthy baby born, and a subset of these women who had a clinical diagnosis of cancer made after the prenatal testing was performed It turned out that 10 women out of the 3757 had a report of cancer subsequently diagnosed Of those women, two were too ill to participate in the study

So we are reporting here on eight women who had a clinical diagnosis of cancer, a healthy baby, and these women all allowed us to look at their medical records, as well as more fully analyze the underlying DNA testing results from their original blood tests When we analyzed their DNA sequencing results, they had DNA imbalances all across the genome The test normally is only looking at DNA material from the chromosomes of clinical interest, chromosomes 13, 18, 21, the X, and the Y When we opened up their results to look at all of the chromosomes, there were multiple abnormalities in other places such as chromosome eight, chromosome 6, et cetera Each woman had a unique pattern that was abnormal in many places

This suggested that it was the tumor DNA that was being shed into her blood and contributing to the abnormal pattern The abnormal pattern really had nothing to do with the baby The conclusion of the study is that maternal cancer, which was asymptomatic at the time of the testing, can be a rare but important cause of discordant, noninvasive, prenatal testing results It's important to recognize that the tumor DNA did not affect the babies in any way All of the babies were born healthy, although one of the babies was born early intentionally to facilitate treatment for the mother

Even though the test is not designed to detect cancer, it incidentally detected cancer, and it's important in the future to understand if there is a prospective cancer signature that can be recognized to improve maternal clinical care There's absolutely no information yet known about the appropriate follow-up for women who have these abnormal patterns that are suggestive of cancer, but this is research that will be done in the future

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