A Blood Test for Cancer


Has a blood test for cancer reached a point where it can be useful clinically? Elizabeth Tracey reports

A blood test looking for modifications to DNA known as methylation is moving closer to usefulness as a screening test for many cancers, a new study finds. William Nelson, director of the Kimmel Cancer Center at Johns Hopkins, says there’s still a ways to go, but this strategy has a good chance of success.

Nelson: And what they found was that when that test suggested that a cancer would be present it was 99.5% specific. And the sensitivity – were they finding all the cancers – was about 67% and seemed to be better if the cancer was at a higher stage. If you had a positive test how likely are you to have a problem and if you have a negative test how easy is it going to be to be for you to sleep at night? Those things are not tested in this model, they’re estimated, they haven’t rigorously tested them.  :29

Nelson says that the test performed best when cancers were advanced, but what is needed in a screening test is one that performs well at very early stages of disease, when the chance for a cure is greatest. He predicts that a blood-based screening test for cancer will be practical in just a couple of years. At Johns Hopkins, I’m Elizabeth Tracey.