By Bill Berkrot NEW YORK | Wed Jun 29, 2011 6:07pm EDT NEW YORK (Reuters) - A landmark study showing that routine lung screening of heavy smokers and former smokers using low dose CT scans could save thousands of lives is sure to set off a fierce debate about the cost of such testing on an overburdened healthcare system. The U.S. National Cancer Institute studied more than 53,000 people between the ages of 55 and 74 deemed at high risk of developing lung cancer. It found that screening with the three-dimensional X-rays cut deaths by 20 percent. Details of the study and a discussion of its implications were published on Wednesday in the New England Journal of Medicine, lending additional weight to initial findings that were released in November. The discussion noted that radiologists using more advanced CT equipment than was available for the study could lead to an even larger reduction in lung cancer deaths. At the same time, the potential for many more false positive results could ri