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Prenatal testing finds mother’s cancer — but CBS lost an opportunity to explain research’s broader relevance


2 Star


Prenatal testing can detect cancer in pregnant mothers

Our Review Summary

Blood testThis CBS story is about the detection of maternal cancers during analysis of DNA blood tests designed to identify chromosomal abnormalities in the fetus. Understandably, the story focuses on the story of a mother who feels her unborn fetus may have “saved her life” because of the unexpected cancer finding. It packs a significant emotional punch for such a very short story and very likely collected a lot of eyeballs. But it missed an opportunity to offer viewers some context and background about the potential risks as well as benefits from wider use of DNA blood tests that reveal incidental findings that suggest disease. The competing WSJ story was longer and provided more of the details we were looking for.


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

In such a short piece, discussions of cost are almost always missing, but they were missing as well in the competing WSJ article.

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

Not Satisfactory

The CBS story says that the study “looked” at eight women. But this is an incomplete description. The study involved 125,426 samples from which abnormal results (typically indicating a chromosomal disorder in the fetus) were detected in 3757 (3%). Ten cancers were subsequently identified in women whose babies were found to be normal despite an abnormal test result, with further analysis done on the eight women mentioned in the story. Without this quantitative data, readers have no sense of the rarity of the eight cases described or of the scope of the benefit that might be realized if such testing were offered more widely.

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

Not Satisfactory

Unlike the WSJ article, there was not even a hint that widespread use of these tests might pose harms as well as benefits, as well as higher costs and ethical dilemmas.

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

Not Satisfactory

The story focuses on the serious impact of the test on a woman’s life and on her ability to “be there” for her child as she battles her cancer. In the sense that this story was more about the potential life-saving aspect of the study for women with hidden cancers, it provides useful information. But so much copy spent on telling the woman’s story meant less space to provide all-important context.  Nothing on the study’s strengths or limitations or what the research means more broadly. For example:  Non-invasive prenatal testing is a new kind of screening test that is sometimes offered to women over 35 or at risk for a child with Down syndrome.  About 3% of women screened have an abnormal result suggesting a fetal abnormality. This was the first large-scale study to confirm that in a small number of such cases, the abnormal test result is caused instead by an undiagnosed cancer in the mother.

Does the story commit disease-mongering?

Not Satisfactory

The story focuses on an individual woman’s story, and provides no perspective on the rarity of her case. Although it may be an underestimate, cancer was reported in only 0.008% of the samples analyzed. The story needed some acknowledgment that this is an exceedingly rare occurrence.

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

Not Satisfactory

The story noted that the study was funded by the manufacturer of the test and that the study author quoted has a relationship with the company. That’s useful context, but we require an independent voice to meet our standard on this criterion. No one was quoted except one of the study’s authors.

Does the story compare the new approach with existing alternatives?

Not Satisfactory

No alternatives to the blood tests were mentioned in any context. The WSJ story, by contrast, notes that the blood tests are now used in place of more invasive amniocentesis or chorionic villus sampling to identify fetuses at risk. The WSJ also underscores the importance of having a positive blood test confirmed with one of these more invasive tests.

Not undergoing testing at all might also be an option, but the story does not address this.

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


Although the availability of these new tests is not specifically addressed, the story does note that “prenatal testing is widely used for pregnant women at risk of having babies with chromosome disorders” — implying that the new tests are one such option. We’ll award a Satisfactory on that basis. The story could also have noted that the new test are recommended by the American College of Obstetrics and Gynecology for some women. Usually they are offered for women over 35 or with other risk factors for a fetus with Down syndrome or certain other chromosomal abnormalities.

Does the story establish the true novelty of the approach?


The story establishes what is new here and made reference to the research done at Tufts and reported in JAMA.

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


The story may have been suggested by a release, but clearly focused almost entirely on interviews with a mother and the principal investigator.

Total Score: 3 of 10 Satisfactory


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