Association between Body Mass Index and Severity According of Classification of Thyroid Cancer

Abstract

1. Abstract 1.1. Purpose: Obesity is associated with aggressive pathological features and poor clinical outcomes in breast and prostate cancers. However, the associations between excess weight and prognostic factors for thyroid cancer are uncertain. This study aimed to evaluate the associations between body mass index (BMI) and severity according of classification of thyroid cancer. 1.2. Methods: Retrospective analysis of 4485 patients with thyroid cancer was performed. Patients were grouped according to BMI (underweight, normal weight, overweight and obesity)-based World Health Organization standardized categories. Clinicopathological factors were analyzed and compared between normal and other groups. 1.3. Results: According to the results, 3789 patients were women (84.5%) and mean age was 47.1 years. 4338 patients (96.7%) were diagnosed with PTC. FTC were 115(2.6%), MTA ware 24(0.5%), ATC were 5(0.1%). There were no significant associations between BMI quartiles and Multifocality, cervical lymph node metastasis, or distant metastasis. Higher BMI were significantly associated with extrathyroidal extension of PTC (P < 0.001). And higher BMI were significantly associated with advanced TNM stage (P=0.005). 1.4. Conclusion: Increased BMI might elevate the risks of aggressive clinicopathological features of PTC, such as extrathyroidal invasion and advanced TNM stage. However, there were few cases except for PTC, which made it difficult to find statistically significant results. To confirm this result, further studies with long-term follow-up and more patients are required. 2. Introduction Recently, the incidence of thyroid cancer has been growing worldwide [1]. Higher prevalence of thyroid cancer can be explained in part by the fact that development and use of neck ultrasonography and ultrasound-guided fine-needle aspiration have led to increased diagnostic rate for asymptomatic thyroid cancer [2]. Additional aspects, such as changes in exposure to environmental factors, may also play a role in explaining such increase in prevalence. However, considering that increase in prevalence of thyroid cancer coincided with increased number of early cancer with small tumor size, as well as various tumor sizes and stages, it is suspected that there are other unidentified factors besides advances in diagnostic tools [3]. The main risk factors for thyroid cancer are exposure to ionizing radiation, a history of benign thyroid disease, and a family history of thyroid cancer [4, 5, 6]. Overweight and obesity, expressed as a high BMI, are possible risk factors for thyroid cancer Obesity is associated with onset and progression of many cancers, including those of esophagus, colon, kidney, breast, skin, rectum, and gallbladder [7]. Obesity is the second most common, preventable, and modifiable cause of carcinogenesis, after smoking, there is worldwide variation that is dependent on the different incidences of obesity [8]. Although obesity is a known risk factor for carcinogenesis it does not seem to equally impact on all types of cancer. However, there are few reports on the relationship between obesity and thyroid cancer and the underlying mechanism is largely unknown [9 -12].