FOR decades, a deadly type of childhood cancer has eluded science’s best tools. Now doctors have made progress with an unusual treatment: Dripping millions of copies of a virus directly into kids’ brains to infect their tumors and spur an immune system attack. A dozen children treated this way lived more than twice as long as similar patients have in the past, doctors reported on Saturday at an American Association for Cancer Research conference and in the New England Journal of Medicine. Although most of them eventually died of their disease, a few are alive and well several years after treatment — something virtually unheard of in this situation. “This is the first step, a critical step,” said the study’s leader, Dr. Gregory Friedman, a childhood cancer specialist at the University of Alabama at Birmingham. “Our goal is to improve on this,” possibly by trying it when patients are first diagnosed or by combining it with other therapies to boost the immune system, he said. The ... » Learn More about Unusual treatment shows promise for cancer