It's Not Too Late

"People who have smoked heavily throughout life can still dramatically cut their risk of lung cancer by quitting, a study has claimed with scientists claiming the finding offers hope to long-term smokers.

The study from the Wellcome Sanger Institute and University College London found that compared to current smokers, people who had quit had more “genetically healthy” lung cells – with the organ growing new healthy cells to replenish the lining of their airways.

The cells in turn were less likely to develop into cancer in the future.
“People who have smoked heavily for 30, 40 or more years often say to me that it's too late to stop smoking - the damage is already done,” Dr Peter Campbell, from the Wellcome Sanger Institute and senior author on the study, said.

"What is so exciting about our study is that it shows that it's never too late to quit - some of the people in our study had smoked more than 15,000 packs of cigarettes over their life, but within a few years of quitting many of the cells lining their airways showed no evidence of damage from tobacco."
Independent