Lifetime smokers should still be encouraged to quit say the authors of a new study showing better survival outcomes for lung cancer patients regardless of how recently they gave up the habit.
In findings presented at the ASCO 2020 Virtual Meeting, Canadian researchers analysed data from 35,428 patients in 17 International Lung Cancer Consortium (ILCCO) studies of whom 47.5% were current smokers, 30% were former smokers, and 22.5% had never smoked at the time of diagnosis.
They found that quitting even within two years of a diagnosis of lung cancer was associated with improved lung cancer survival across all stages, histologies and independent of other prognostic factors.
Among all former smokers, those who quit for less than two years before diagnosis had a hazard ratio of 0.88 for overall survival compared to current smokers. The corresponding risk reductions for people who quit, between two to five years before, and for more than five years before a lung cancer diagnosis were 16% and 20%.
The benefits of quitting were slightly greater among heavy smokers (more than 30 pack years).
In terms of lung cancer specific survival a reduction of 15% was seen among patients who had quit more than five years prior to diagnosis. The adjusted hazard ratios for quitting two to five years before diagnosis were 0.93 and 0.95 respectively, both non-significant.
“This research shows that if you’re a smoker and you quit, no matter when you quit, you will be more likely to survive after being diagnosed with lung cancer, compared to someone who continues smoking,” said lead author Dr Aline Fusco Fares, clinical research fellow at Princess Margaret Cancer Centre in Toronto.
“The study’s message is simple: quit smoking now.”
The researchers said lung cancer screening offers an opportunity to encourage heavy smokers to quit.
They noted that long-term heavy smokers who quit for less than two years before, between two to five years before, and for more than 5 years before their lung cancer diagnosis had 14%, 17%, and 22% respective reduced risks of death from all causes, compared to current smokers.
Commenting on the findings, ASCO President Dr Howard Burris, the results should provide additional incentive for smokers – particularly those who have smoked for many years – to quit.
“The improvements in survival seen even with quitting a short time before lung cancer diagnosis show that it’s never too late to stop smoking,” he said.