Reversal of risk after quitting smoking.

B46

The International Agency for Research on Cancer convened a Working Group in March 2006 to review the scientific evidence on the reversal of risk for adverse health effects upon quitting smoking. Seventeen experts from eight countries assessed the changes in risk for smoking-related cancers, cardiovascular diseases and chronic obstructive lung disease after smoking cessation. The Working Group examined the scientific evidence to answer three questions: 1. Is the risk for disease lower in former smokers than in continuing smokers?; 2. What is the time course of the reduction in risk with continued abstinence?, and 3. Does the risk return to that of never-smokers after long periods of abstinence? With respect to tobacco-related cancers, published studies show a lower risk for lung cancer in former smokers within five to nine years after cessation, which further decreases compared to that of current smokers upon longer periods of abstinence. Cessation in middle age results in a substantially lower risk for lung cancer compared to stopping at an older age. However, the absolute annual risk for developing lung cancer in former smokers does not decrease after cessation; there is persistent increased risk in relation to never-smokers. The risk for laryngeal cancer decreases steeply with time since cessation, by approximately 60% within 10-15 years after cessation but remains increased compared to that of never-smokers. The relative risk for oral and pharyngeal cancer decreases with increasing duration of abstinence compared with that of continuing smokers and remains higher than in never-smokers until the second decade of abstinence, reaching the level of never-smokers thereafter. Pancreatic, stomach, liver, renal, bladder and cervical cancers were similarly examined and substantial decreases in risk after smoking cessation were observed. Quitting smoking results in significant health benefits that accrue with increasing duration of abstinence for several tobacco-related cancers.