Progress on New Blood Test for Cancer

Researchers are making progress on a blood test that can spot a single cancer cell among a billion healthy ones.

The health care company Johnson & Johnson says it will join scientists at Massachusetts General Hospital, where the test was invented, to try to bring the test to market within the next several years.

Researchers think the test has the potential to transform care of many types of cancer, especially breast, colon, prostate and lung.

Doctors hope to use it to determine what treatment would be best for a particular tumor, and to find out quickly if the treatment is working.

Ultimately, the test may offer another way to screen for cancer besides the mammograms, colonoscopies and other methods used now. But that will require more study.