The Holy Grail in the brain tumor field, according to Mayfield Clinic neurosurgeon Dr. Ron Warnick, would be a non-invasive test allowing personalized therapy, a way to reliably distinguish if the tumor has grown back, and the ability to make a very specific prognosis. This blood test is still in the research stage. WVXU's Ann Thompson, in "Focus on Technology," reports how it would work and the hope that it carries.