The overall survival advantage was significant regardless of how long ago patients had last smoked, including among those who quit within 2 years prior to their diagnosis.
These findings create a "teachable moment" for health care providers in scenarios when patients might be more receptive to a stop-smoking message, said researcher Aline F. Fares, MD, a clinical research fellow at Princess Margaret Cancer Centre in Toronto.
"Our study can be summarized to patients as, ‘it’s never too late to quit,' " Fares said.
She presented results from this study at the American Society of Clinical Oncology virtual scientific program during a press briefing in advance of the meeting.
Fares presented data on 35,481 patients with a diagnosis of lung cancer who had been enrolled in 17 studies conducted by the International Lung Cancer Consortium.
At diagnosis, 47.5% of the patients were current smokers, 30% were former smokers, and 22.5% were never smokers.
The risk of death from any cause was cut by 20% among former smokers who quit more than 5 years before their lung cancer diagnosis . Patients who quit smoking 2-5 years before diagnosis had a 16% reduction in the risk of death, while those who quit within 2 years of diagnosis had a 12% reduced risk.
The overall survival advantage was evident regardless of sex, disease stage, histology, or amount of smoking as measured in pack-years, according to Fares. That said, the overall survival advantage appeared to be even greater among heavier smokers -- greater than 30 pack-years -- as compared with lighter smokers.
Lung cancer–specific survival was improved by 15% for patients who quit smoking more than 5 years prior to their diagnosis. For those who had quit more recently, there was a nonsignificant trend toward improvement in this outcome.
Overall survival was higher in never smokers in comparison with current smokers, a finding that was expected based on previous studies, Fares said.
These findings could be important to share with individuals who are current smokers at the time of lung cancer screening, said Maher A. Karam-Hage, MD, medical director of the tobacco treatment program at the University of Texas MD Anderson Cancer Center, Houston.
"The power of this data is that it shows quitting makes a difference, and that it can be more impactful the longer you quit before you get diagnosed," Karam-Hage said.
Negative lung cancer screening results sometimes give individuals the false impression that they are "one of the lucky ones" who won’t get lung cancer and don’t have to quit smoking, said Karam-Hage, who is studying the comparative effectiveness of different smoking cessation strategies.
"Now, as part of shared decision making, we can provide people with specific numbers before the scan that [suggest] no matter what the scan comes out with, the earlier they quit, the better off they will be," he said.
In her presentation, Fares said that lung cancer screening may be an "interesting time" to address smoking cessation, particularly among patients with a heavier smoking history.
"After a lifetime of smoking, patients often feel it’s too late to quit smoking and that the damage has already been done," she said.
The International Lung Cancer Consortium studies had multiple supporters. Fares reported having no disclosures related to the research. One researcher reported relationships with AbbVie, AstraZeneca, MedImmune, Bayer, Bristol-Myers Squibb, Merck, Novartis, Pfizer, Roche Canada, and Takeda. Karam-Hage reported having no relevant disclosures.