In preparation for minor surgery, John Leventhal needed a routine chest x-ray.When the New Haven, CT, doctor joined the radiologist who was examining the film, he was shocked by what he saw: an opaque blotch deep in his lung. "As a physician," says Leventhal, "you're taught in medical school that when you see a mass like that, it means lung cancer." Leventhal's medical training also taught him that to confirm the diagnosis, his doctors would need to crack open his rib cage to get a piece of the suspect tissue that would be closely examined by a pathologist-an extremely painful and hazardous operation. The weekend before that surgery, Leventhal went off on a family ski vacation. He recalls thinking, "This is the last time I will go skiing for a long, long time."

That was five years ago. Today the medical profession's way of dealing with cancer could be about to change. Around the same time that Leventhal underwent
surgery, researchers at Stanford University and Santa Clara, CA-based startup Affymetrix were beginning to build the first "DNA microarrays."More commonly known as DNA chips, these are DNAcovered silicon, glass or plastic wafers capable of analyzing thousands of genes at a time to, for example, identify the ones that are active in a sample of cells. Now these microarrays appear poised to join the war on cancer. DNA chips, predicts National Cancer Institute director Richard Klausner, are "going to have a huge effect" on the diagnosis and treatment of the disease.