Discordant NIPT Test Results May Reflect Presence of Maternal Cancer
News Jul 14, 2015
Illumina, Inc. has announced that a preliminary study retrospectively correlated 10 cases of occult maternal cancer among pregnant women receiving an “aneuploidy detected” or “aneuploidy suspected” positive results on the verifi® noninvasive Prenatal Test (NIPT)1 to discordant results of fetal karyotypes for the women, suggesting that discordant NIPT test results may be indicative of maternal cancer.
Maternal cancers sometimes leave tell-tale abnormal cell free DNA fragments in plasma. In 8 of 10 reported cancer cases, Illumina scientists and physicians reviewed all the genome-wide sequencing data and identified nonspecific copy-number changes across multiple chromosomes, suggesting that these changes, when present in a woman whose fetal karyotype tests as normal, might represent a signal to the clinician to probe for the presence of cancer.
The results of the study, entitled “Noninvasive Prenatal Testing and Incidental Detection of Occult Malignancies,” are available online in The Journal of the American Medical Association and the full article can be accessed at broadcast.jamanetwork.com. The paper will be included in the July 14 print edition of JAMA.
“Abnormal tumor DNA, shed from maternal malignancies, can cause highly unusual NIPT results, including the findings of more than one chromosome abnormality detected,” commented Diana W. Bianchi, M.D., Executive Director of the Mother Infant Research Institute at Tufts Medical Center, and lead author of the publication. “All abnormal NIPT results should be confirmed with a diagnostic test, such as amniocentesis or chorionic villus sampling (CVS). If there is a difference between the fetal diagnostic test and the NIPT results, maternal cancer can be a rare but important underlying explanation. In order to provide the best maternal clinical care, this possibility should be considered, especially when multiple abnormalities of chromosome number are identified on the NIPT report.”
In a retrospective analysis of 125,426 noninvasive verifi® Prenatal Tests, 3,757 (three percent) were positive for one or more aneuploidies involving chromosomes 13, 18, 21, X or Y. As part of Illumina’s standard procedures, the laboratory contacts the referring physician to discuss all positive test results and to recommend a diagnostic procedure to obtain a confirmatory fetal karyotype.
From this group of 3757 positive cases, 10 cases of maternal cancers were subsequently (between 3 and 39 weeks after NIPT) reported to the laboratory. At the time of NIPT these women were not diagnosed with cancer. In 3 cases the abnormal NIPT findings prompted a search for an underlying malignancy. Seven of these eight women had diagnostic tests that indicated a chromosomally-normal fetus, discordant with the NIPT test result. One woman did not undergo a diagnostic procedure.
Maternal cancers were most frequently associated with the rare NIPT finding of multiple aneuploidies that were discordant with the fetal karyotype. The cancer types were clinically diverse, including three cases of B cell lymphoma and single cases of T-cell leukemia, Hodgkin’s lymphoma, unspecified adenocarcinoma, leiomyosarcoma, and neuroendocrine, colorectal and anal carcinomas. The cancers ranged from stage II to metastatic disease (IV). In one case, after completion of treatment, the abnormal DNA signature became undetectable in follow-up testing.
“This study shows that NIPTs that use whole genome sequencing techniques may have the ability to detect some cancer signatures under certain conditions,” said Dr. Rick Klausner, Illumina’s Chief Medical Officer. “The sensitivity and specificity of the verifi Prenatal Test to detect cancer is not currently known, and further studies will be required to develop a test for this specific purpose. We have published these results to help clinicians improve overall patient care by considering the possibility of maternal cancer if there is discordance between positive NIPT results and a normal fetal karyotype. We also want to encourage health care providers to contact the clinical sequencing laboratory with follow-up information on abnormal NIPT results that show concordance as well as discordance with fetal karyotype, including cancers diagnosed in pregnant women, so that we can better understand the nonspecific patterns of DNA changes that precede clinical symptoms.”