Influence of smoking cessation after diagnosis of early stage lung cancer on prognosis: systematic review of observational studies with meta-analysis

To systematically review the evidence that smoking cessation after diagnosis of a primary lung tumour affects prognosis.

Systematic review with meta-analysis. DATA SOURCES: CINAHL (from 1981), Embase (from 1980), Medline (from 1966), Web of Science (from 1966), CENTRAL (from 1977) to December 2008, and reference lists of included studies. STUDY SELECTION: Randomised controlled trials or observational longitudinal studies that measured the effect of quitting smoking after diagnosis of lung cancer on prognostic outcomes, regardless of stage at presentation or tumour histology, were included. DATA EXTRACTION: Two researchers independently identified studies for inclusion and extracted data. Estimates were combined by using a random effects model, and the I(2) statistic was used to examine heterogeneity. Life tables were used to model five year survival for early stage non-small cell lung cancer and limited stage small cell lung cancer, using death rates for continuing smokers and quitters obtained from this review.