Can a simple blood test really predict breast cancer?

BMJ 2012; 344 doi: 10.1136/bmj.e3374 (Published 15 May 2012)

Cite this as: BMJ 2012;344:e3374

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Margaret McCartney, general practitioner, Glasgow

margaret@margaretmccartney.com

Media coverage of a complex paper looking at epigenetic markers for breast cancer was widespread but too simplistic. Are the tests accurate and useful, asks Margaret McCartney, and where is the discussion of the potential harms?

The Radio 4 Today programme heralded a day of wall to wall epigenetics. “Every now and then a new word emerges from scientific journals that lay people have to get used to. Such a word is epigenetics,” said presenter John Humphrys. Changes within genes resulting from environmental factors that may be linked to breast cancer “may be able to be detected early, many years before the cancer develops,” he explained.

James Flanagan, the corresponding author of the study under discussion, was asked about the implications and agreed that it was a breakthrough. “We’ve found something that we can detect before breast cancer develops, so as a risk marker, this is really what we want to find.” People with a high level of abnormalities are at high risk.

Humphrys asked, “So you’re going to be able, potentially, fairly soon, to be able to assess the level …