More Americans now qualify for yearly scans to detect lung cancer, according to guidelines released Tuesday that may help more Black smokers and women get screened. Lung cancer is the nation’s top cancer killer, causing more than 135,000 deaths each year. Smoking is the chief cause and quitting the best protection. Usually, lung cancer is diagnosed too late for a good chance at survival. But some Americans who are at especially high risk get an annual low-dose CT scan, a type of X-ray, to improve those odds.