Scientists are reporting progress against a deadly type of childhood cancer with an unusual treatment. It involves putting viruses directly into the brain to spur an immune system attack. The therapy is for gliomas, tumors that are almost always fatal after they recur following usual treatments. A dozen children treated this way lived more than twice as long as similar patients have in the past. Doctors reported on the treatment over the weekend at a cancer conference and in the New England Journal of Medicine. Most of the children eventually still died of their disease but several have lived several years. Doctors are fine-tuning the approach to try to improve survival.