Prenatal Testing May Also Detect Some Maternal Cancers

A new bioinformatics study shows that prenatal genetic test results, such as revealed by noninvasive prenatal testing (NIPT) for fetal chromosome abnormalities, may also detect underlying conditions in the mother, including cancer.

Diagnosis of cancer during pregnancy is relatively uncommon (incidence about 1 in 1,000 women). A team of scientists and clinicians, led by Diana W. Bianchi, MD, of Tufts Medical Center (Boston, MA, USA) and the Reproductive and Genetic Health Expert Advisory Panel at Illumina (Redwood City, CA, USA), has reported results of their genome-wide analysis performed on available DNA sequencing data for a case series of 8 women with abnormal NIPT results. Analysis showed discordance with the fetal karyotype: while their fetuses had normal chromosomes, retrospective genomic analysis showed that the abnormal results were due to a variety of undiagnosed cancers in the mothers. The findings demonstrate that previously undetected maternal cancers may provide a biological explanation for some differences between results from prenatal diagnostic versus prenatal screening tests.

NIPT is a recent clinical advance that provides pregnant women with information about possible chromosomal abnormalities, such as Down syndrome, in their fetuses. The screening test, which can be offered as early as the 10th week of pregnancy, analyzes fragments of placental and maternal DNA that circulate in maternal plasma. In women with cancer, the plasma sample also contains cancer DNA.

“This study provides one explanation for when NIPT results are different from the fetal karyotype. It highlights the need to perform a diagnostic procedure to determine true fetal karyotype whenever NIPT suggests chromosomal abnormalities,” said Dr. Bianchi, expert on NIPT.

The 8 cases in this preliminary study of occult malignancy came from 125,426 samples submitted from asymptomatic pregnant women who underwent NIPT for fetal chromosomal abnormalities, of which 3757 cases were positive for one or more abnormalities in the number of chromosomes 13, 18, 21, X, or Y. The women’s physicians later reported 10 cases of cancer to the laboratory that originally conducted the NIPT, the study analyzed 8 of these in depth. All of the women had abnormal NIPT results, and most frequently, more than one chromosomal abnormality was detected, a very unusual result. Cancer was diagnosed during pregnancy or postpartum in these women at an average of 16 weeks following the initial NIPT. The clinical importance of these findings will require further research.

“NIPT results may lead to findings of an underlying maternal condition, which, in these cases, was due to cancer,” said Dr. Bianchi, “The take-home message is that women should be aware of this possibility when they seek testing. More research needs to be done to further study this occurrence to help guide physicians on how to counsel women and manage their follow-up care.”

The study, by Bianchi DW, et al, was published July 14, 2015, in the Journal of the American Medical Association (JAMA).

Related Links:
Tufts Medical Center
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