Prenatal blood test detects cancer in mothers-to-be

US company Sequenom has revealed that its prenatal blood test - MaterniT21 PLUS - has detected potential cancer in at least 40 expectant mothers since its launch three years ago.

The non-invasive prenatal test looks at DNA circulating in the mother's bloodstream to identify certain chromosomal abnormalities in the developing fetus. But because the test cannot distinguish between maternal and fetal DNA, it has inadvertently picked up genetic abnormalities in several women, leading to 26 confirmed cancer diagnoses.

At the Future of Genomic Medicine conference in La Jolla, California last week, anaesthesiologist Dr Eunice Lee, 40, told the audience how she had chosen to take the test because of her age. However, she was surprised when, instead of informing her about her baby's genetics, her doctor advised her to undergo a whole-body MRI to look for malignancy.

'The director of the laboratory called my obstetrician and told her I needed to be worked up for cancer, which was just alarming, to her and also to myself, because I had no idea I had cancer,' said Dr Lee.

The subsequent tests revealed a seven centimetre tumour in Dr Lee's colon, which she immediately underwent surgery for. In November, she gave birth to a healthy baby boy.

'I just felt like I was the luckiest person in the world,' Lee said. 'In my case, the test probably saved my life.'

The findings lend weight to a future for so-called 'liquid biopsies' in detecting cancer through routine blood tests - something that several companies, including Sequenom, are looking to explore. However, they also raise new legal and ethical issues around the use of non-invasive prenatal tests, which are not intended for cancer diagnostics and are not regulated by the US Food and Drug Administration (FDA).

BuzzFeed News science editor, Virginia Hughes, explains that the companies that make the tests are caught between the risk of being sanctioned for providing cancer diagnostics from an unlicensed test and the ethical imperative to pass on the information to women so that they can seek a proper diagnosis.

'It’s a funny spot for the lab to be in,' Laura Hercher, a genetic counselor at Sarah Lawrence College in New York state, told Hughes. However, she added that on the other hand, 'it's really hard, ethically, to make the case that you should sit on this information'.

Additionally, the rate of false positives - an important consideration for any diagnostic test - is currently unknown. False positive results can risk a woman undergoing invasive procedures or receiving radiation or chemotherapy unnecessarily.

In the meantime, Sequenom is using what it has learned from these unexpected findings in the development of new tests specifically for cancer. Dirk van dem Boom, the company's chief scientific officer, told BuzzFeed News: 'We’re getting a glimpse of what the technology can do.'

The findings come in the same week that Sequenom announced a net income of US$18.3 million for quarter four of 2014 after reporting a loss for the same period last year. The company also made a profit of 14 cents per share after being forecast a loss of five cents per share.