While most similar studies compare mortality rates between current smokers and never smokers, the majority of study participants were ex-smokers, allowing researchers to focus on the effects of quitting smoking.
Smoking History and Lung Cancer Survival Rates
The study followed 5,594 patients with NSCLC, who accounted for 85% of all lung cancer cases, enrolled in the Massachusetts General Hospital Boston Lung Cancer Survival Cohort between 1992 and 2022. Of these participants, 795 had never smoked; 3308 people are ex-smokers; 1491 people were currently smokers. Participants filled out questionnaires about their smoking habits and other health and demographic information at baseline, and the researchers checked their survival every 12 to 18 months. During the study period, 3,842 participants died: 79.3% of current smokers, 66.8% of former smokers, and 59.6% of never smokers.
Although never smoking was associated with increased survival after lung cancer diagnosis, the findings showed a significant association between lower mortality and smoking before diagnosis. The longer a patient was smoke-free, the greater the health benefits: For ex-smokers, doubling the number of years they quit smoking before being diagnosed with lung cancer was significantly associated with longer survival.
The researchers noted that the association between survival and smoking history may differ depending on the clinical stage at which lung cancer is diagnosed, and that the study did not take into account the different treatments participants received.
Other co-authors from the Harvard Chan School included Xinan Wang, Christopher Romero-Gutierrez, and Jui Kothari. Funding for the study came from National Cancer Institute grant 5U01CA209414.