Trends in Prevalence of Thyroid Cancer Over Three Decades: A Retrospective Cohort Study of 17,526 Surgical Patients.

ABSTRACT

INTRODUCTION: Thyroid cancer (TC) incidence has been increasing in recent years. The aim of this study was to investigate our institution-based estimates of operative volumes for TC over the last three decades. MATERIALS AND METHODS: This was a retrospective cohort study of patients undergoing thyroid surgery at our institution. Patient characteristics were reviewed in three subgroups Group I (treated in 1981-1986), Group II (treated in 1987-2002), and Group III (treated in 2003-2012). RESULTS: TC was diagnosed in 1578/17,526 (9.0%) thyroid operations. Incidence of TC increased from 3.7% in Group I to 10.4% in Group III (p < 0.001). Incidence of papillary TC increased form 40.6% in Group I to 81.3% in Group III (p < 0.001). In the latter group, 23.5% of all papillary TCs were diagnosed in patients with Hashimoto's disease. Meanwhile, incidence of anaplastic TC decreased from 16.2% in Group I to 2.1% in Group III patients (p < 0.001). pT1 tumors were diagnosed in 8.1% Group I and 54.8% Group III (p < 0.001), whereas pT4 tumors were identified in 40.5% Group I, 2.4% Group II, and 0.84% Group III subjects (p < 0.001). pT3 tumors were found in 51.6% Group I, whereas multifocal papillary TCs were found in 15.7% Group III patients, the latter with a higher prevalence of pN1 stage (p < 0.001). CONCLUSIONS: The following trends in surgical volume for TC were identified throughout the study period a fivefold increase of thyroid operations for TC, a threefold increase in incidence of papillary TC, and an eightfold decrease in incidence of anaplastic TC. It is of interest that a significant increase in incidence of multifocal papillary TC in young female patients with Hashimoto's disease was found over time.