Although it is well understood that tobacco smoking profoundly impacts lung cancer risk, data are limited about the extent to which smoking cessation prior to diagnosis affects overall survival and lung cancer–specific survival. Lung cancer screening offers a teachable moment, but there is uncertainty about the nature of smoking cessation benefits after a lifetime of smoking. Researchers used the International Lung Cancer Consortium (ILCC) database to learn whether smoking cessation prior to lung cancer diagnosis is associated with better overall survival and lung cancer–specific survival, considering time since smoking cessation.
Analysis was performed using data from 17 ILCC studies with available time since smoking cessation to estimate survival. Of 35,428 patients in the database, 41% were current smokers, 41% were ex-smokers, and 18% were never smokers at the time of diagnosis with lung cancer.
Ex-smokers and never smokers had improved overall survival compared with current smokers (adjusted hazard ratio [aHR], 0.76; confidence interval [CI], 0.73-0.80). Among ex-smokers, those who quit <2 years ago (aHR, 0.88; CI, 0.82-0.94), between 2 and 5 years ago (aHR, 0.83; CI, 0.77-0.90), and >5 years ago (aHR, 0.8; CI, 0.76-0.84) had improved overall survival compared with current smokers.
Sensitivity analysis showed a trend toward improved lung cancer–specific survival for those who quit smoking <2 years ago (aHR, 0.95; CI, 0.86-1.05) and those who quit 2 to 5 years ago (aHR, 0.93; CI, 0.83- 1.04). In contrast, patients who quit >5 years ago had significantly improved lung cancer–specific survival (aHR, 0.85; CI, 0.78-0.92).
To mimic lung cancer screening participants, researchers analyzed data from 30+ pack-years patients. Associations between time since smoking cessation and survival were striking: patients who quit smoking <2 years ago had improved overall survival by 15% (aHR, 0.86; CI, 0.80-0.93). Patients who quit 2 to 5 years ago had improved overall survival by 17% (aHR, 0.83; CI, 0.76-0.90) and >5 years ago had improved overall survival by 22% (aHR, 0.78; CI, 0.74-0.83), compared with current smokers.
For less than 30 pack-years patients, a trend toward better overall survival was observed for those who quit within 2 years (aHR, 0.95; CI, 0.92-1.02) and 2 to 5 years (aHR, 0.86; CI, 0.74-1.01). Patients who quit smoking >5 years ago had improved overall survival by 23% (aHR, 0.77; CI, 0.72-0.82).
Among ex-smokers, risk of death was reduced by 12% if patients quit within 2 years, 17% for those who quit 2 to 5 years ago, and 20% for those who quit smoking >5 years ago. For lung cancer–specific survival, the benefit was significant only for those who quit >5 years ago compared with patients who smoked at the time of diagnosis.
These data suggest that convincing patients who undergo screening to quit smoking at any point of their trajectory, even within 2 years prior to diagnosis, improves their overall survival. Lung cancer–specific survival benefit was present beyond 5 years of quitting. These relationships are independent of pack-years and age, and were seen across all disease stages and other prognostic variables.
- Fares AF, Jiang M, Yang P, et al. Smoking cessation and lung cancer outcomes: a survival benefit for recent-quitters? A pooled analysis of 34,649 International Lung Cancer Consortium patients. J Clin Oncol. 2020;38:suppl (abstract 1512).