“A new type of blood test is starting to transform cancer treatment, sparing some patients the surgical and needle biopsies long needed to guide their care.
“The tests, called liquid biopsies, capture cancer cells or DNA that tumors shed into the blood, instead of taking tissue from the tumor itself. A lot is still unknown about the value of these tests, but many doctors think they are a big advance that could make personalized medicine possible for far more people.
“They give the first noninvasive way to repeatedly sample a cancer so doctors can profile its genes, target drugs to mutations, tell quickly whether treatment is working, and adjust it as the cancer evolves.
“Two years ago, these tests were rarely used except in research. Now, several are sold, more than a dozen are in development, and some doctors are using them in routine care.”