“A large, international study reported by researchers at the Princess Margaret Cancer Centre gives smokers one more major incentive to quit. Those who stop smoking cigarettes improve their chances of survival after being diagnosed with lung cancer – even if they quit as recently as within two years of a diagnosis. Most people are familiar with the commonly recognized benefits of quitting smoking: decreased risks of getting heart disease, lung disease, and developingvarious cancers. But this is the first study that shows a distinct survival benefit for former smokers after receiving a lung cancer diagnosis.

Researchers analyzed data from 17 International Lung Cancer Consortium studies on 35,428 patients with lung cancer, of which 47.5 per cent were current smokers, 30 per cent were former smokers, and 22.5 per cent had never smoked at the time of diagnosis.

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Because of its novel and important public health message, it has been rated one of the top studies to be presented at the prestigious American Society of Clinical Oncology (Virtual) Annual Meeting this month.  

One of the long-standing public health questions that this study answers is: "Does quitting smoking now, impact a person's survival if they are diagnosed with lung cancer later?" explains senior co-author and Clinician Scientist Dr. Geoffrey Liu, the Director of the Lung-CALIBRE (Lung Cancer And Liquid biopsy, Informatics, Breathomics, and Radiomics for Early detection) Program at Princess Margaret Cancer Centre. 

"It's never too late to quit," emphasizes Dr. Liu, who is also a lead investigator of the Lusi Wong Early Detection of Lung Cancer Program.

"If you quit now, and you get lung cancer, you'll have a higher chance of living longer," says Dr. Liu, who also holds also holds the Alan B. Brown Chair in Molecular Genomics and is a Professor of Medicine, Medical Biophysics, and Epidemiology, and Professor at the Dalla Lana School of Public Health, University of Toronto (U of T). 

"With this study, we are eliminating more and more reasons for why some smokers may still hesitate to quit." Lead author Dr. Aline Fusco Fares, a clinical research fellow at the Princess Margaret under the supervision of Dr. Liu, adds: "The study's message is simple: quit smoking now." Both Drs. Fares and Liu also noted that the message is timely, as the Princess Margaret is one of four pilot sites across Ontario assessing how best to roll out organized lung cancer screening for people at high risk. "Screening gives us the chance to educate and empower smokers with as much information as possible to help motivate them to quit," says Dr. Fares. 

In the study, the researchers found that among all former smokers, those who quit for less than two years before a lung cancer diagnosis, had a 12 per cent reduced risk of death from all causes, when compared to current smokers. Those who quit between two years and five years before a diagnosis had a 16 per cent reduced risk of death; while those who quit for more than five years before a diagnosis had a 20 per cent reduced risk of death from all causes. The benefit to quitting smoking was slightly greater among those who had smoked at least 20 cigarettes per day for more than 30 years.

Also contributing to the study as senior co-author is Wei Xu, PhD, a Clinician Scientist at the Princess Margaret, and an Associate Professor in Biostatistics at U of T's Dalla Lana School of Public Health.

Funding for this research is from the Alan B. Brown Chair, the Lusi Wong Fund, the Posluns Family Fund, CCSRI, Ontario Health (Cancer Care Ontario), Natural Sciences and Engineering Research Council of Canada and the Division of Medical Oncology and Hematology – Dr. Ronald Feld Fellowship.”