Among patients diagnosed with non-small cell lung cancer, the most common form of lung cancer, research led by scientists from the Harvard Chan School of Public Health, published online in the journal JAMA Network Open, found that those with , not only those who have never smoked, but also those who stopped smoking in time.

While most research has compared mortality between current smokers and non-smokers, the new study focused on ex-smokers to investigate what happens after smoking cessation.

The study included 5,594 Massachusetts General Hospital patients from 1992-2022 with non-small cell lung cancer, which represents 85% of all lung cancer cases. Of these, 795 had never smoked, 3,308 were ex-smokers and 1,491 current smokers. During the study period, 79.3% of current smokers, 66.8% of ex-smokers and 59.6% of non-smokers died.

Although never having smoked was associated with a better chance of survival after a lung cancer diagnosis, the findings showed significant association between lower mortality and smoking cessation prior to diagnosis. Current smokers had a 68% higher mortality and ex-smokers had a 26% higher mortality compared to non-smokers.

The longer a patient remained smoke-free, the greater the benefits to his health. For ex-smokers, doubling the years of smoking cessation before diagnosis was significantly associated with prolonged survival. Conversely, doubling years of smoking was associated with shorter survival among current and former smokers diagnosed with lung cancer.

The researchers note, however, that the association between survival and smoking history may vary depending on the clinical stage at which the lung cancer was diagnosed, and that the study did not take into account the different types of treatment participants were receiving.