Are we outsmarting cancer? Or just ourselves? Over the past several years, scientists have begun looking not just for individual genes linked to cancer, but for collections of genes and molecules, like proteins, that form telltale patterns, or signatures, that can be used to identify a cancer cell and reveal what drugs might kill it. Signatures can be used to diagnose the disease, scientists hope, and to give a prognosis to patients who have cancer. But there have been few successes in this brave new world of cancer research, and some notable failures. Genetic tests devised at Duke University by researchers using the new methodology have turned out to be worthless, though they were once hailed as breakthroughs. Two new blood tests for ovarian cancer have also been abandoned. Despite the setbacks, researchers say they cannot give up on their quest for cancer signatures.