For decades, the search for cancer has required a different test for each disease — a colonoscopy here, a mammogram there — leaving vast territories of the body unexamined. This week, a panel of federal advisers moved medicine closer to a different possibility: a single blood draw capable of listening for the molecular whispers of dozens of cancers at once. The FDA's advisory committee voted to endorse Galleri, a test developed by Grail, finding sufficient evidence that detecting cancer early through circulating DNA can translate into genuine benefit for patients who feel no symptoms at all. T