Associations Between Body Mass Index And Clinico-pathological Characteristics Of Papillary Thyroid Cancer:a Retrospective Study

Objective:The incidence of papillary thyroid cancer has been growing throughout the world during recent decades.Epidemiological studies suggest that obesity is associated with an increased risk of thyroid cancer.However,the associations between excess weight and prognostic factors for thyroid cancer are uncertain.We evaluated the relationships between body mass index(BMI)and clinico-pathological features and outcomes of papillary thyroid cancer(PTC).Methods: Retrospective analysis of 796 patients with PTC was performed.We used logistic regression models to estimate odds ratios(OR)with 95% confidence intervals(CI)to define associations between increasing BMI and clinico-pathological features of PTC.Logistic regression model was also used to analyze the differences of clinical cases between groups,in which the normal weight group was used as control group.Non-parametric test was used to compare overweight group and obesity group with normal weight group for the difference of cervical lymph node metastasis.Results:In this study,796 patients were enrolled,the proportion of female patients and male patients was about 3:1,the average age of the patients was(46.2±11.5)years old,and the average body mass index was(25±3.40)kg/m2.A 5-kg/m2 increase in BMI was associated with PTC tumours larger than 1 cm(odds ratio(OR)= 1.267,P=0.027),with extrathyroidal invasion(OR=2.201,P=0.001),with Multifocality(OR=1.31,P=0.01)and with advanced tumour-node-metastasis(TNM)stage(OR=1.479,P=0.004),which is independent of confounding variables such as gender,age,serum TSH,total cholesterol and fasting glucose level.The OR [95% confidence intervals(CI)] in the overweight and obese groups for tumours larger than 1cm were 1.53(CI:1.14-2.06,P=0.005)and 1.96(CI:1.15-3.34,P=0.014),respectively,compared to the normal weight group.The OR [95% confidence intervals(CI)]in the overweight and obese groups for extra-thyroidal invasion were 2.42(CI:1.78-3.3,P<0.001)and 4.23(CI:2.4-7.3,P<0.001),respectively,compared to the normal weight group.The OR(95% CI)for lateral neck LNM in the obesity group was1.92(1.12-3.27,P=0.017),and the OR for advanced TNM stage in the overweight group was1.83(1.33-2.52,P<0.001)compared to the normal weight group.Further analysis of the relationship between BMI and cervical lymph node metastasis by nonparametric test shown that the number of positive central and lateral cervical lymph nodes in overweight group more than that in the normal weight group and the difference was statistically significant(P=0.014?P=0.05);the number of positive central and lateral cervical lymph nodes in obesity group more than that in the normal weight group and the difference was statistically significant(P=0.013?P=0.017).Conclusion: Higher BMI was strongly associated with aggressive features of PTCs such as larger tumour size,extra-thyroidal invasion and cervical lymph node metastasis.Patients with high body mass index(BMI)had an advanced TNM stage the first time to see a doctor.This study suggests that excess weight and obese patients of PTC should have active treatment options.Further studies with long-term follow-up are needed to confirm this finding.