Rising Incidence of Small Size Papillary Thyroid Cancers with No Change in Disease-Specific Survival in Finnish Thyroid Cancer Patients

BACKGROUND: The aim of this study was to investigate trends in the incidence, diagnostics, treatment and survival of thyroid cancer in Tampere University Hospital (TAUH) region in recent decades. MATERIAL AND METHODS: New thyroid cancer cases from 1981 to 2002 were ascertained from the Finnish Cancer Registry. Follow-up data was collected from medical records of TAUH. Differentiated thyroid cancer (DTC; consisting of papillary thyroid cancer (PTC) and follicular thyroid cancer (FTC)) patients' data was analyzed and divided into two equal time periods (1981-1991 and 1992-2002). RESULTS: The total amount of thyroid cancer cases was 553, of which 427 (77%) were papillary and 72 (13%) follicular. Thyroid cancer was four times more common in females than in males and the median age at the time of diagnosis was 52 years. The incidence of DTC was 4.5/100,000 in the earlier group and 6.0/100,000 in the later group (IRR 1.33, CI 1.11-1.60). The proportion of papillary thyroid cancer rose from 81% to 89% (p=0.02) in two study periods. Median tumour size became smaller, from 25 mm to 15 mm (p<0.001). Surgery became more radical as total thyroidectomies were performed almost exclusively on the later group (p<0.001). Median cumulative dose of radioiodine (I131) therapy was higher in the later group (p=0.04). There was no difference in number of cancer recurrences (p=0.54). The prognosis of DTC was good; 10-year disease-specific survival was 92% in the earlier group and 94% in the later group (p=0.43). CONCLUSIONS: The incidence of thyroid cancer has risen and proportion of papillary cancer has increased, however, median size of tumour has decreased. No difference was seen in either all-cause or disease-specific survival.