Prenatal test accidentally picks up cancer in 50% of those with wonky results

To address the lack of data, researchers at the National Institute of Health set up a study to look at outcomes after abnormal cfDNA tests—and specifically look for cancer in patients. Women were enrolled if they were pregnant or recently postpartum and had no known cancers. Another big requirement was that they had received some perplexing cfDNA result, such as an unreportable result or an abnormal result that didn’t match a healthy fetus or secondary genetic test results, like the woman’s case in 2013.

Fresh data

For the study, published Wednesday in the New England Journal of Medicine, NIH researchers set out to repeat the cfDNA tests and then screen the women for cancer using various methods. Those included family and clinical histories, blood tests, measurements of serum tumor markers, fecal occult blood tests, pap smears, physical exams, and—the big one—whole-body magnetic resonance imaging (MRI).

In all, 107 women were enrolled. Of those, 52 (48.6 percent) were found to have hidden cancers. Thirty-two participants had blood cancers (31 were lymphomas), while 20 had solid tumors, including breast, bile duct, colorectal, pancreatic, lung, kidney, bone, and adrenal gland cancers.

Of the 52 with cancer, 29 (55.8 percent) had no symptoms of their disease. Thirteen had cancer symptoms that were ascribed to pregnancy-related causes. For example, stomach pain from pancreatic cancer was diagnosed as reflux. Ten had symptoms that were either overlooked by the woman or were evaluated but deemed not concerning.

Of the 20 cases with solid tumors, most were in later stages (five were stage 2 or 3, and 13 were stage 4). But of the 20 cases overall, 13 were eligible for potentially curative treatments.

Then there were the other 55 women who had no detectable cancer. Of those, researchers concluded that 15 had simply gotten a rotten cfDNA result, which they based on repeat cfDNA testing and the cancer screens. Thirty were found to have noncancerous biological reasons for their weird cfDNA results, including fibroids, placental mosaicism, a stem cell abnormality, or a fetal finding. But, the remaining 10 had no clear explanation for their odd cfDNA results, stumping the researchers. These participants are now being followed for five years to assess their outcomes.