Blood test for cancer?

There's a new test that is so sensitive it can find one cancer cell in a billion. Veridex and Johnson & Johnson's Ortho Biotech Oncology unit will work on making the test more inexpensive. They'll start a research center at Massachusetts General Hospital. That hospital as well as Sloan-Kettering, University of Texas M.D. Anderson Cancer Center in Houston and Dana-Farber Cancer Institute in Boston will start using the test this year. If you could find out quickly, "this drug is working, stay on it," or "this drug is not working, try something else," that would be huge, Dr. Daniel Haber, chief of Mass General's cancer center and one of the test's inventors, told the Associated Press. It will take five years of testing before the procedure will be on the market.

It will be able to detect one cancer cell that's broken off from a tumor and wending its way through your bloodstream. And then what will it do?