RT Journal Article
SR Electronic
T1 Lung cancer, genetic predisposition and smoking: the Nordic Twin Study of Cancer
JF Thorax
JO Thorax
FD BMJ Publishing Group Ltd and British Thoracic Society
SP 1021
OP 1027
DO 10.1136/thoraxjnl-2015-207921
VO 72
IS 11
A1 Hjelmborg, Jacob
A1 Korhonen, Tellervo
A1 Holst, Klaus
A1 Skytthe, Axel
A1 Pukkala, Eero
A1 Kutschke, Julia
A1 Harris, Jennifer R
A1 Mucci, Lorelei A
A1 Christensen, Kaare
A1 Czene, Kamila
A1 Adami, Hans-Olov
A1 Scheike, Thomas
A1 Kaprio, Jaakko
A1 
YR 2017
UL http://thorax.bmj.com/content/72/11/1021.abstract
AB Background We aimed to disentangle genetic and environmental causes in lung cancer while considering smoking status.Methods Four Nordic twin cohorts (43 512 monozygotic (MZ) and 71 895 same sex dizygotic (DZ) twin individuals) had smoking data before cancer diagnosis. We used time-to-event analyses accounting for censoring and competing risk of death to estimate incidence, concordance risk and heritability of liability to develop lung cancer by smoking status.Results During a median of 28.5 years of follow-up, we recorded 1508 incident lung cancers. Of the 30 MZ and 28 DZ pairs concordant for lung cancer, nearly all were current smokers at baseline and only one concordant pair was seen among never smokers. Among ever smokers, the case-wise concordance of lung cancer, that is the risk before a certain age conditional on lung cancer in the co-twin before that age, was significantly increased compared with the cumulative incidence for both MZ and DZ pairs. This ratio, the relative recurrence risk, significantly decreased by age for MZ but was constant for DZ pairs. Heritability of lung cancer was 0.41 (95% CI 0.26 to 0.56) for currently smoking and 0.37 (95% CI 0.25 to 0.49) for ever smoking pairs. Among smoking discordant pairs, the pairwise HR for lung cancer of the ever smoker twin compared to the never smoker co-twin was 5.4 (95% CI 2.1 to 14.0) in MZ pairs and 5.0 (95% CI 3.2 to 7.9) in DZ pairs.Conclusions The contribution of familial effects appears to decrease by age. The discordant pair analysis confirms that smoking causes lung cancer.