The more people smoke, the longer they smoke, and the earlier they start smoking, the more likely they are to develop lung cancer. Smokers of two or more packs a day have lung cancer mortality rates 15 to 25 times greater than non-smokers.
If smokers stop smoking before cancer has started, their lung tissue tends to repair itself, even if there were already precancerous changes. Former smokers who haven’t smoked for 15 or more years have lung cancer mortality rates only somewhat above those for non-smokers.
