Factors Determining Risk Categories in Differentiated Thyroid Carcinoma: Study of an Indian Cohort

INTRODUCTION: Differentiated thyroid carcinoma/cancer (DTC) burden in developing countries could be different from that of the developed nations. AIMS AND OBJECTIVES: To describe the clinicopathological characteristics in a cohort of DTC patients in a south Indian state of Kerala and to compare with the data from other centres. MATERIALS AND METHODS: A retrospective analysis of the data collected on DTC patients, from January 2010 to August 2018, attending thyroid cancer clinic at a tertiary care centre. RESULTS: mong the 944 patients (male 262; female 682; mean age 43.8 years; standard deviation, SD 13.8), types of tumour were as follows: classical papillary thyroid carcinoma (cPTC) 48.3%, follicular variants of PTC (FVPTC) 28.8%, follicular and hurthle cell carcinoma (FTC&HCC) 10.1%. Mean size of the tumour was 2.7 cm (SD 1.8) papillary thyroid micro carcinomas (PTMC) were seen in 113 patients (12%), which were detected incidentally. Metastases were present at diagnosis in 40.2% cases, most common site being cervical lymph nodes. Distant metastases were seen in 113 patients (14.5%) and commonest site was bone. The American Thyroid Association (ATA) risk stratification was possible only in 684 subjects and showed 31.3% low risk, 41.8% intermediate risk and 26.9% at high-risk category. Lymph node metastasis and distant metastasis were the commonest determining factors for intermediate and high-risk category, respectively. High-risk category was significantly higher in patients >55 years, tumour size >4 cm, FTC/HCC tumour type and extranodal extension (ENE) of lymph node metastasis. Radio active iodine ablation was given to 85.2% subjects. CONCLUSION: In our DTC population, FVPTC formed the second most common type and PTMC were all incidentalomas. Metastasis at diagnosis was higher suggesting delayed presentation. Old age, FTC/HCC, large size of the tumour, ENE were significantly higher in high-risk patients. Rest of the features of these cohort was comparable with the United States cohort of DTC patients.