Lung Cancer Risk Among Heavy Smokers Who Quit

Even among former smokers who have not smoked in more than 15 years, there is more than a minimal risk of lung cancer.

It is well known that the risk of developing lung cancer decreases after smoking cessation; however, current lung cancer screening guidelines are based on former smokers who have quit smoking for 15 years or less. Smokers with more than 15 years since quitting have been excluded from the guidelines, and information about the risk of lung cancer in this group is limited.

Researchers led by Hilary Tindale, MD, MPH, from Vanderbilt University in Nashville, analyzed data from the Framingham Heart Study and assessed lifetime smoking and lung cancer incidence. Heavy smokers were defined as those having more than 21.3 pack-years of smoking history.

At the median follow-up of 28.7 years, 284 lung cancers had been detected. Incidence rates per 1000 person-years were 1.97 in current smokers, 1.61 in former smokers, and 0.27 in those who had never smoked.

Heavy former smokers had a 39.1% lower lung cancer risk within 5 years since quitting compared with current smokers; however, among all former smokers, 40.8% of lung cancers occurred after more than 15 years since quitting.

The researchers concluded that although the risk of lung cancer decreases within 5 years of quitting, 4 of 10 lung cancers in this study population occurred in former smokers with more than 15 years since quitting, which is beyond the screening window of current guidelines.

Even among long-time (>15 years) former smokers, there is more than a minimal risk of lung cancer.