Tobacco smoking and risk of thyroid cancer according to BRAF V600E mutational subtypes.
Smoking has been associated with reduced risk of thyroid cancer, but whether the association varies between higher- and lower-risk cancers remains unclear.We recruited 1013 people diagnosed with thyroid cancer and 1057 population controls frequency matched on age and sex. Multivariable logistic regression was used to assess the association overall and in analyses stratified by tumor characteristics. We used sensitivity analysis to assess the potential for selection bias.We found little evidence of an association with current smoking (odds ratio [OR] = 0.93; 95% confidence interval [CI] 0.69-1.26; current vs. never smoking), but a higher number of pack-years of smoking was associated with lower risk of thyroid cancer (OR = 0.75; 95% CI 0.57-0.99; ≥ 20 pack-years vs. never). However, after correcting for potential selection bias, we observed a statistically significant inverse association between current smoking and risk of thyroid cancer (bias-corrected OR = 0.65; 95% CI 0.51-0.83). Those with BRAF-positive cancers were less likely to be current smokers than those with BRAF-negative cancers (prevalence ratio [PR] = 0.79; 95% CI 0.62-0.99).We found smoking was inversely related to thyroid cancer risk and, in particular, current smoking was associated with a reduced risk of potentially more aggressive BRAF-positive than the likely more indolent BRAF-negative papillary thyroid cancers. This article is protected by copyright. All rights reserved.
Authors: Sabbir T Rahman, Nirmala Pandeya, Rachel E Neale, Donald S A McLeod, Peter D Baade, Philippa H Youl, Roger Allison, Susan Leonard, Susan J Jordan