Primary prevention, smoking, and smoking cessation: implications for future trends in lung cancer prevention.

BACKGROUND: Cigarette smoking is the major cause of lung cancer, and most lung cancers have historically occurred among current cigarette smokers or recent quitters. The relative risk of developing lung cancer declines in former smokers to approximately twice that of never smokers after 20 years of cessation, but it remains elevated indefinitely. As an increasing fraction of those who have ever smoked become former smokers, the absolute risk of lung cancer in the population will decline; and an increasing fraction of lung cancer cases will occur among former smokers.
METHODS: Data from the 12-year follow-up of American Cancer Society Cancer Prevention Study I are used to estimate lung cancer death rates for smokers, never smokers, and former smokers by duration of cessation. These estimates are combined with population-based estimates of smoking status by birth cohort to generate models of lung cancer death rates for current and former smokers.
RESULTS: Modeled estimates of lung cancer death rates suggest that, in the near future, the majority of lung cancer cases will be occurring among former smokers.
CONCLUSIONS: Former smokers already have acted on the advice of their physicians to reduce their lung cancer risk; however, they will generate an increasing fraction of the cancers that are seen. Approaches must be developed for these former smokers to alter their risk if lung cancer death rates are going to continue to be affected. Additional primary preventive strategies, including chemoprevention, offer hope to these former smokers, as do secondary preventive efforts, such as screening.