While often studies compare outcomes for smokers vs. never smokers, investigators found that quitting smoking earlier also was beneficial.
Among people diagnosed with the most common type of lung cancer, called non-small cell lung cancer, current smokers had 68% higher numbers of deaths compared to never smokers, while former smokers had only 26% higher numbers of deaths.
And the longer a patient had quit smoking before being diagnosed with lung cancer, the better the odds of survival.
“Our participants’ smoking histories varied, with some having stopped smoking a few years before their diagnosis and others having stopped several decades before,” said senior study author David Christiani, a professor of environmental genetics at Harvard T.H. Chan School of Public Health in Boston.
“This wide range gave us confidence in our results -- that the benefit of pre-diagnosis smoking cessation persists even after lung cancer is diagnosed," he said in a university news release.
The researchers studied nearly 5,600 patients with this common lung cancer who were enrolled in the Boston Lung Cancer Survival Cohort at Massachusetts General Hospital between 1992 and 2022.
Among them, 795 had never smoked, 3,308 were former smokers and 1,491 were current smokers.
Each participant answered questions about their smoking habits and other health and demographic information at the beginning of the study. Researchers checked on their survival every 12 to 18 months.
During the study period, 3,842 of the participants died, including 79.3% of the current smokers, 66.8% of the former smokers and 59.6% of the never smokers.
Of course, never smoking gave individuals the best odds of survival, but still researchers noted significant associations between lower numbers of deaths and having quit smoking before being diagnosed with lung cancer.
Doubling the number of years they had quit before their lung cancer diagnosis was significantly associated with prolonged survival.
The associations between survival and smoking history may vary depending on the clinical stage at which lung cancer was diagnosed, the researchers noted. Also, the study did not account for the different kinds of treatment participants were receiving.
Funding for the study came from U.S. National Cancer Institute. Results were published online May 5 in the journal JAMA Network Open.
The U.S. Centers for Disease Control and Prevention has tips on how to quit smoking.
SOURCE: Harvard T.H. Chan School of Public Health, news release, May 5, 2023
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