BOSTON (AP) - Scientists in Boston have announced they're teaming up with Johnson & Johnson to bring a new cancer test to market.

The blood test is so sensitive it can spot a single cancer cell among a billion healthy ones. Many doctors think stray cancer cells in the blood mean that a tumor has spread or is likely to spread.

Four big cancer centers will start studies this year using the experimental test, which could potentially transform care for many types of cancer.

Initially, doctors want to use the test to try to predict what treatments would be best for each patient's tumor and find out quickly if they are working.

One of the inventors of the test says it's "like a liquid biopsy." Dr. Daniel Haber of Massachusetts General says it can avoid the painful sampling of tissue. And he says it could be a better way of monitoring patients than periodic imaging scans.