A blood test for cancer
People usually find out that they have cancer through screenings or after symptoms start showing – but these sorts of signs often appear only after the cancer has spread so much that it can't be treated.
What if you could find out from a simple, highly accurate blood test that you had an incipient tumor? ScienceNOW asks.
Researchers from Johns Hopkins have sequenced the abnormal DNA that a tumor releases into the bloodstream, bringing us another step closer to a universal cancer test.
Previous research on cells shed into the blood by tumors – as well as free-floating tumor DNA in blood -- have shown:
No matter the type of cancer, tumor cells almost invariably have substantially altered chromosomes, such as swapped pieces and extra copies of certain genes. This suggests that a test that could detect any chromosomal abnormalities in a person's blood could serve as a general test for cancer.
- First, the team isolated the free DNA in blood samples from 10 people with advanced colon or breast cancer.
- Then, using whole-genome sequencing technology, they read the entire genome of the DNA in the blood.
- To find tumor-associated sequences, they had to sift through large amounts DNA from normal cells floating in blood. Turns out, the portion of DNA from tumors ranged from 47.9 percent to as low as 1.4 percent.
They found that the cancer patients all had DNA with chromosomal alterations in their blood. None of 10 healthy controls tested positive.
The method could help track a patient's tumor regrowth or response to treatment. It could also help decide what drug a patient should take without having to do a biopsy. Some patients in this research have extra copies of two genes known to drive cancer -- ERBB2 and CDK6 -- which can be targeted with existing drugs.
Each test in this study cost several thousand dollars and took a month. But as sequencing costs decrease, the test could eventually be useful for early detection. A test like this could reach the clinic within 5 years.
The work was published in Science Translational Medicine a couple weeks ago.
Image: Science Translational Medicine/AAAS