Association among Body Mass Index, Genetic Variants of FTO, and Thyroid Cancer Risk: A Hospital-Based Case-Control Study of the Cancer Screenee Cohort in Korea

Obesity has been determined to be associated with fat mass and obesity-associated (FTO) gene and thyroid cancer risk. However, the effect of combined interactions between obesity and the FTO gene on thyroid cancer needs further investigation. This study aimed to examine whether interactions between body mass index (BMI) and the FTO gene are associated with an increased risk of thyroid cancer. A total of 705 thyroid cancer cases and 705 sex- and age-matched normal controls were selected from the Cancer Screenee Cohort in National Cancer Center, Korea. A conditional logistic regression model was used to calculate the odds ratios (ORs) and 95% confidence intervals (CIs) for the measure of associations and the combined effect of BMI and FTO gene on thyroid cancer. BMI was associated with an increased risk of thyroid cancer in subclasses of overweight (23-24.9 kg/m2; adjusted OR, 1.50; 95% CI, 1.12 to 2.00) and obese (≥ 25 kg/m2) (adjusted OR, 1.62; 95% CI, 1.23 to 2.14). There were positive associations between the FTO genetic variants rs8047395 and rs8044769 and an increased risk of thyroid cancer. Additionally, the combination of BMI subclasses and FTO gene variants was significantly associated with thyroid cancer risk in the codominant (rs17817288), dominant (rs9937053, rs12149832, rs1861867, and rs7195539), and recessive (rs17817288 and rs8044769) models. Findings from this study identified the effects of BMI on thyroid cancer risk among individuals carrying rs17817288, rs9937053, rs12149832, rs1861867, rs7195539, and rs8044769, whereas the effects of BMI may be modified according to individual characteristics of other FTO variants.