A blood test so sensitive that it can spot a single cancer cell lurking among a billion healthy ones is moving one step closer to being available at your doctor's office.
Boston scientists who invented the test and health care giant Johnson and Johnson were expected to announce today that they are joining forces to bring it to market.
Four big cancer centres also will start studies using the experimental test this year.
Stray cancer cells in the blood mean that a tumour has spread or is likely to, many doctors believe.
A test that can capture such cells has the potential to transform care for many types of cancer, especially breast, prostate, colon and lung.
Initially, doctors want to use the test to try to predict what treatments would be best for each patient's tumour and find out quickly if they are working.
"This is like a liquid biopsy" that avoids painful tissue sampling and may give a better way to monitor patients than periodic imaging scans, said Dr Daniel Haber, chief of Massachusetts General Hospital's cancer centre and one of the test's inventors.
Ultimately, the test may offer a way to screen for cancer besides the mammograms, colonoscopies and other less-than-ideal methods used now.
Many people have their cancers diagnosed through needle biopsies.
These often do not provide enough of a sample to determine what genes or pathways control a tumour's growth. Or the sample may no longer be available by the time the patient gets sent to a specialist to decide what treatment to prescribe.
Doctors typically give a drug or radiation treatment and then do a CT scan two months later to look for tumour shrinkage.
Some patients only live long enough to try one or two treatments, so a test that can gauge success sooner could give patients more options.
The new test uses a microchip that resembles a lab slide covered in 78,000 tiny posts, like bristles on a hairbrush. The posts are coated with antibodies that bind to tumour cells.
When blood is forced across the chip, cells ping off the posts like balls in a pinball machine. The cancer cells stick, and stains make them glow so researchers can count and capture them for study.