“Other doctors felt they could not operate,” says Sean O’Brien, an astrocytoma survivor. But MD Anderson neurosurgeon Frederick Lang, M.D., successfully removed Sean’s brain tumor.

During Sean’s sophomore year of college, he began experiencing intense headaches and other symptoms. “I couldn’t sleep properly, I stopped going to classes, and if I moved too quickly, my vision would go out,” recalls Sean, now 30. “I’d get tunnel vision...