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Thoughtful and thorough coverage on prenatal tests’ ability to find cancer in mothers


5 Star

Prenatal Blood Tests Could Detect Cancer in Mothers

Our Review Summary

Blood testThis Wall Street Journal story offers a thoughtful and thorough summary of a presentation (and related study in JAMA) about the ability of commercial prenatal blood tests to also uncover hidden cancers in pregnant women. The story makes clear that the study’s finding of “rare cases” of cancer “underscores both challenges and opportunities” for the tests, particularly those related to the tests’ potential to reveal elevated risks for future diseases. Other stories, including one from CBS News, focused more viscerally on the handful of mothers whose hidden cancers were detected by the fetal blood work. While stories focusing on such vignettes may pack a significant emotional punch, they also may leave readers with an exaggerated sense of these tests’ cancer-finding ability and the risk that most women face. As demonstrated by the WSJ coverage, there are many ethical and social issues raised by widespread DNA testing that also merit discussion.


Why This Matters

There is increasing demand by physicians and pregnant women to perform noninvasive prenatal blood tests as a safer means of establishing fetal risk for Down Syndrome and other serious genetic abnormalities. Although professional guidelines suggest that only women at high risk of carrying fetuses with serious genetic abnormalities get these tests, they are already widely used because other procedures, such as amniocentesis, can occasionally lead to miscarriage. The discovery that in a few rare cases, the abnormalities detected in the tests have nothing to do with the fetus, but with a mother’s undiagnosed cancer instead, will likely lead to even more demand for use of these tests. That poses not only the ethical problem of whether and when to divulge incidental genetic risks also uncovered in maternal DNA (say, of breast cancer), but also a potential explosion of costs related to use of the blood tests to screen every pregnant woman to find a very small number of cancers.



Does the story adequately discuss the costs of the intervention?

Not Satisfactory

Although the story does not explicitly note the cost of the two commercially available tests, it does provide substantial context about the rising popularity of the tests among clinicians and pregnant women, as well as cautionary notes about their use from both those involved in the study and an expert who wrote an accompanying editorial to the JAMA article.

Does the story adequately quantify the benefits of the treatment/test/product/procedure?


The story clearly explains that the eight cases of maternal tumor DNA findings came from a collection of more than 125,000 blood samples submitted to one of the companies over a two-year period, and that about 3 percent were positive for one or more chromosomal abnormalities. It also points out that follow-up tests showed the fetus was normal in a “very small number of instances” and that among those just 10 cases of maternal cancer were suspected. Further, of the eight women featured in the published report, just three had their cancers diagnosed because of the findings.

The story earns a Satisfactory grade here. Some additional questions that could have been addressed by the coverage include:

  • Precisely how often do these blood tests find genetic abnormalities when the fetus is, in fact, normal? (The story says this occurs in “a very small number of instances,” but it’d be useful to put a number on it?)
  • Are such cases always indicative of maternal cancer? If not, what other conditions might trigger an abnormal result?
  • Are there false-positives? In other words, could women with an inaccurate positive result be subjected to additional costly/invasive tests to find a cancer that doesn’t even exist?

Does the story adequately explain/quantify the harms of the intervention?


The WSJ article very explicitly notes that there are harms from invasive prenatal tests, although it does not give rates of miscarriage; and it goes into welcome detail about the challenges of giving women genetic risk information for themselves or their infants based on the noninvasive blood test, noting “there is no consensus on when or how to inform” patients of such findings. On the other hand, the story explains, if maternal tumor DNA is detected, the need to inform the mother may be urgent and life saving.

Does the story seem to grasp the quality of the evidence?


The story gets a passing grade here. It adequately describes the study and notes appropriately that “the full implications of the new findings need further study.” Some discussion of the strengths and limitations of the study design, and what additional information is needed to inform clinical practice related to these tests, would have been welcome complements to the coverage.

Does the story commit disease-mongering?


The story never suggests that fetal chromosomal abnormalities or maternal cancers uncovered by the blood tests are a major threat. Unlike the CBS story, WSJ notes that the cases identified in the study were culled from more than 100,000 samples and that such findings are “rare.” The tone of the story is cautious and it quotes experts who call for further studies and conversations about the current and potential use of diagnostic prenatal blood testing.

Does the story use independent sources and identify conflicts of interest?

Not Satisfactory

The story importantly refers to “ongoing debates” within the medical and scientific community about the wider use of the blood tests, and quotes an editorial written by an expert who did not participate in the study itself. However, while the story notes that the study was funded by Illumina, which markets the test, it did not alert readers that Dr. Bianchi, the study author who is quoted in the piece, is a paid advisor to the company. CBS, by contrast, made note of that relationship. We reluctantly grade the story Not Satisfactory based on that omission.

Does the story compare the new approach with existing alternatives?


The article explains nicely the major alternatives to the fetal blood tests and also mentions both companies that market the test.

Does the story establish the availability of the treatment/test/product/procedure?


Again, the story could have benefited from some cost information about the tests and whether they are covered by most insurance plans. It also would have benefited from a sentence about how women can best arrange for such testing, and how widely available they are at prenatal clinics and private practices. But it does give information about the total number of tests done in the U.S. and about their growing popularity.

Does the story establish the true novelty of the approach?


The story points out that the findings are new and serendipitous, then ties them in nicely to the broader issue of maternal and fetal DNA testing and the serious debate about testing’s  benefits and potential harms.

Does the story appear to rely solely or largely on a news release?


There was a JAMA release on the study, but the story also appears to be solidly based on a presentation at a scientific society meeting and the JAMA article and accompanying editorial.


Total Score: 8 of 10 Satisfactory


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