Influence of smoking cessation after diagnosis of early stage lung cancer on prognosis: systematic review of observational studies with meta-analysisBMJ 2010; 340 doi: http://dx.doi.org/10.1136/bmj.b5569 (Published 22 January 2010) Cite this as: BMJ 2010;340:b5569
- A Parsons, research fellow1,
- A Daley, senior lecturer, NIHR career scientist2,
- R Begh, research associate1,
- P Aveyard, clinical reader, NIHR career scientist1
- 1UK Centre for Tobacco Control Studies, Primary Care Clinical Sciences, University of Birmingham, Edgbaston, Birmingham B15 2TT
- 2Primary Care Clinical Sciences, University of Birmingham
- Correspondence to: A Parsons
Objective To systematically review the evidence that smoking cessation after diagnosis of a primary lung tumour affects prognosis.
Design 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 I2 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.
Results In 9/10 included studies, most patients studied were diagnosed as having an early stage lung tumour. Continued smoking was associated with a significantly increased risk of all cause mortality (hazard ratio 2.94, 95% confidence interval 1.15 to 7.54) and recurrence (1.86, 1.01 to 3.41) in early stage non-small cell lung cancer and of all cause mortality (1.86, 1.33 to 2.59), development of a second primary tumour (4.31, 1.09 to 16.98), and recurrence (1.26, 1.06 to 1.50) in limited stage small cell lung cancer. No study contained data on the effect of quitting smoking on cancer specific mortality or on development of a second primary tumour in non-small cell lung cancer. Life table modelling on the basis of these data estimated 33% five year survival in 65 year old patients with early stage non-small cell lung cancer who continued to smoke compared with 70% in those who quit smoking. In limited stage small cell lung cancer, an estimated 29% of continuing smokers would survive for five years compared with 63% of quitters on the basis of the data from this review.
Conclusions This review provides preliminary evidence that smoking cessation after diagnosis of early stage lung cancer improves prognostic outcomes. From life table modelling, the estimated number of deaths prevented is larger than would be expected from reduction of cardiorespiratory deaths after smoking cessation, so most of the mortality gain is likely to be due to reduced cancer progression. These findings indicate that offering smoking cessation treatment to patients presenting with early stage lung cancer may be beneficial.
We thank Anne Fry-Smith, senior information specialist for the West Midlands Health Technology Appraisal Collaboration (WMHTAC) and the Aggressive Research Intelligence Facility (ARIF) at the University of Birmingham, for support in developing the search strategies, and Jon Deeks, professor of health statistics, and Roger Holder, senior lecturer in statistics, at the University of Birmingham for statistical support.
Contributors: All authors identified studies for inclusion and extracted data. AP did the analysis and drafted the paper, which was edited by AD, RB, and PA. AP is the guarantor.
Funding: The work was undertaken by the UK Centre for Tobacco Control Studies, a UKCRC Public Health Research centre of excellence. Funding came from the British Heart Foundation, Cancer Research UK, Economic and Social Research Council, Medical Research Council, and National Institute for Health Research, under the auspices of the UK Clinical Research Collaboration. PA and AD are supported by National Institute for Health Research career scientist fellowship awards. The views expressed in this publication are those of the authors and have not been influenced by the funding bodies.
Competing interests: PA has done consultancy work for the manufacturers of smoking cessation drugs. AP has been reimbursed by Pfizer for attending a conference.
Ethical approval: Not needed.
Data sharing: Technical appendix including the search strategies, Stata commands, and life table calculations available from the corresponding author.
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