Quitting Smoking at Any Point, Even Close to a Lung Cancer Diagnosis, Improves Chances of Survival

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For immediate release
May 13, 2020

ASCO Perspective
“We’ve been encouraging people to quit smoking for a long time. These results add more weight to this public health message and 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,” said ASCO President Howard A. Burris III, MD, FACP, FASCO. 

ALEXANDRIA, Va. — People who quit smoking at any time — even less than 2 years before a lung cancer diagnosis — improve their chances of survival after being diagnosed with the disease, according to the results of a large international study that will be presented during the virtual scientific program of the 2020 American Society of Clinical Oncology (ASCO) Annual Meeting. 

Study at a Glance


How soon after smoking cessation do survival benefits start to accrue after a lung cancer diagnosis


35,428 patients with lung cancer from studies from an international consortium of lung cancer researchers 


Former smokers who quit for less than 2 years before, between 2-5 years before, and for more than 5 years before a lung cancer diagnosis had, respectively, a 12%,16% and 20% reduced risk of death from all causes, when compared to current smokers. 


No matter when smokers quit, their chance of survival increases following a lung cancer diagnosis.

Key Findings
The researchers found that among all former smokers, those who quit for less than 2 years before, between 2-5 years before, and for more than 5 years before a lung cancer diagnosis had, respectively, a 12%,16% and 20% reduced risk of death from all causes, when compared to current smokers. The benefit to quitting smoking was slightly greater among those who had smoked at least 20 cigarettes per day for more than 30 years. 

Tobacco smoking profoundly impacts lung cancer risk. Lung cancer is the leading cause of cancer mortality, making up almost 25% of all cancer deaths, and it is estimated that smoking causes 8 out of 10 lung cancers deaths. While much is known about how smoking cessation affects the risk of developing lung cancer, there has been uncertainty about how soon after smoking cessation survival benefits start to accrue after a lifetime of smoking. 

“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 Aline Fusco Fares, MD, who is a clinical research fellow at Princess Margaret Cancer Centre in Toronto. “The study’s message is simple: quit smoking now.”  

About the Study
The researchers analyzed data from 17 International Lung Cancer Consortium (ILCCO) studies that included data on time to smoking cessation. The consortium is an international group of lung cancer researchers who aim to share comparable data from ongoing lung cancer case-control and cohort studies.  

This analysis included 35,428 patients with lung cancer, of which 47.5% were current smokers, 30% were former smokers, and 22.5% had never smoked at the time of diagnosis.  

The study results showing decreased risk of death after lung cancer diagnosis for former smokers include deaths from all causes. 

“Although we can’t say that all these deaths after a lung cancer diagnosis are specifically due to the disease, a proportion of them certainly are,” said senior author, Geoffrey Liu, MSc, MD, who is a clinician scientist at the Princess Margaret Cancer Centre in Toronto. 

There was evidenced by a trend toward improved lung cancer-specific survival for those who quit smoking less than 2 years before and between 2-5 years prior to diagnosis. Improvement in lung cancer-specific survival was statistically significant for those who quit smoking for more than 5 years prior to diagnosis. 

Lung cancer screening offers an opportunity to encourage smokers to quit. With this in mind, the researchers next looked at long-term, heavy smokers — those who smoked more than 30 pack-years — as these smokers would likely be included in lung cancer screening recommendations. A pack year is defined as the equivalent of 20 cigarettes (a standard pack of cigarettes) smoked every day for one year. 

Long-term heavy smokers who quit for less than 2 years before, between 2-5 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. This effect was not as strong for those who smoked less than for < 30 pack-years; the reduction rate was significant only for those who had quit at least 5 years before diagnosis (23%). 

“We saw a slightly bigger benefit to quitting among people who had smoked heavily for over 30 years compared with the overall population of former smokers. For long-term smokers, the benefits of quitting cannot be overstated,” said Dr. Liu. 

Next Steps
The researchers plan to collaborate with local lung cancer screening programs to incorporate the findings from this study into a pilot program of smoking cessation counsellng sessions. 

ILCCO studies have multiple supporters, including Alan Brown Chair in Molecular Genomics, National Cancer Institute grants, the Intramural Research Program of the Center for Cancer Research, Mayo Foundation, etc. 

View the disclosures for the 2020 Cancer Communications Committee: https://www.asco.org/sites/new-www.asco.org/files/content-files/about-asco/pdf/2020-am-ccc-disclosures.pdf

View the disclosures for Dr. Burrishttps://coi.asco.org/share/UK4-3LNB/Howard%20Burris 

Media Contact: Rachel Cagan

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Founded in 1964, the American Society of Clinical Oncology, Inc. (ASCO®) is committed to making a world of difference in cancer care. As the world’s leading organization of its kind, ASCO represents nearly 45,000 oncology professionals who care for people living with cancer. Through research, education, and promotion of the highest-quality patient care, ASCO works to conquer cancer and create a world where cancer is prevented or cured, and every survivor is healthy. Conquer Cancer, the ASCO Foundation, supports the Society by funding groundbreaking research and education across cancer’s full continuum. Learn more at www.ASCO.org, explore patient education resources at www.Cancer.Net, and follow us on Facebook, Twitter, LinkedIn, Instagram, and YouTube.