A new study suggests that it’s never too late to quit smoking to reverse tobacco damage and possibly prevent cancer. 

Quitting appears to reawaken healthy cells, triggering the airways to regrow a new lining, said Peter Campbell, Ph.D., and colleagues from the Wellcome Sanger Institute, United Kingdom.

“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,” he reported.

While some smoking damage is irreversible, the finding is very hopeful, the researchers wrote. Compared to continuing smokers, participants who quit had four times the number of genetically healthy lung cells. And those cells have a much lower risk of becoming cancerous, they said.

The study shows that “it really is worth quitting smoking to reduce the risk of lung cancer,” concluded Sam Janes, Ph.D., from University College London.

Full findings were published online this week in the journal Nature.