Prognostic factors of papillary and follicular thyroid cancer: differences in an iodine-replete endemic goiter region

Abstract

Papillary (PTC) and follicular thyroid carcinoma (FTC) are known as differentiated thyroid carcinoma (DTC). Nevertheless, according to the UICC/AJCC (TNM) classification PTC and FTC are frequently analyzed as one cancer. The aim of this study is to show differences in outcome and specific prognostic factors in an iodine-replete endemic goiter region. Six hundred and three patients with DTC treated within a 35-year-period were retrospectively analyzed with respect to carcinoma-specific survival. Prognostic factors were tested for their significance using univariate and multivariate analysis. The histological type (PTC versus FTC) was found to be a highly significant factor - carcinoma-specific survival both in univariate (P<0.001) and multivariate analyses (P=0.003) was significantly different. Univariate analysis revealed patients' age, extra-thyroid tumor spread, lymph node and distant metastases, increasing tumor size, and the tall cell variant to be significant prognostic factors for PTC patients. Age > or =45 years, positive lymph nodes and increasing tumor size were confirmed as independent prognostic factors. Univariate analysis of FTC patients revealed age at presentation, gender, extrathyroidal tumor spread, lymph node and distant metastases, increasing tumor size, multifocality, widely invasive tumor growth and oxyphilic variant to be factors bearing prognostic significance. The presence of distant metastases and increasing tumor size could be identified as independent prognostic factors for FTC patients. This study shows distinctive differences in prognostic factors of PTC and FTC: independent factors predicting poor prognosis are age > or =45 years, positive lymph nodes and increasing tumor size for PTC, and distant metastases and increasing tumor size for FTC. PTC and FTC patients should be analyzed and reported separately.