Cigarette smoking and thyroid cancer risk: A Mendelian randomization study

Area of Science:

• Genetics
• Epidemiology
• Oncology

Background:

• The association between cigarette smoking and thyroid cancer is debated.
• Previous studies reported conflicting results regarding this relationship.

Purpose of the Study:

• To investigate the causative impact of smoking on thyroid cancer incidence using Mendelian randomization.
• To clarify the controversial relationship between smoking and thyroid cancer.

Main Methods:

• Utilized Mendelian randomization with genetic variants from large-scale genome-wide association studies (GWAS) for smoking phenotypes.
• Included data from the Genome-wide association study and Sequencing Consortium of Alcohol and Nicotine use and UK Biobank.
• Analyzed thyroid cancer outcomes from the FinnGen GWAS, employing sensitivity analyses like weighted median and MR-PRESSO.

Main Results:

• No statistically significant evidence was found linking smoking initiation, cigarettes per day, or past tobacco smoking to thyroid cancer.
• Instrumental variable analysis (IVW) showed no causal effect (e.g., OR=1.56, p=0.61 for smoking initiation).
• Heterogeneity and pleiotropy tests confirmed the validity of the Mendelian randomization estimates.

Conclusions:

• Mendelian randomization analysis indicates no causal link between smoking exposure and elevated thyroid cancer incidence.
• The findings do not support a causative role of smoking in the development of thyroid malignancies.