Changing trends in incidence and mortality of thyroid cancer in Scotland.

Objective: The incidence of thyroid cancer is increasing in several countries. The aim was to investigate trends in the incidence and mortality of thyroid cancer in Scotland, where thyroid cancer is relatively uncommon, between 1960 and 2002.

Design: Descriptive epidemiological study.

Methods: Thyroid cancer registrations between 1960 and 2000 were obtained from the Scottish Cancer Registry. Mortality data (1960-2002) and population estimates were supplied by the Registrar General for Scotland. Incidence and mortality data are expressed as age-specific rates and European age-standardized rates (EASRs).

Results: Thyroid cancer was three times more common in females than in males and was more common in older than younger age groups. Between 1960 and 2000, the annual EASR of thyroid cancer increased from 1.76 to 3.54 per 100,000 for females (P < 0.001) and from 0.83 to 1.25 per 100,000 in males (P < 0.001). The overall thyroid cancer increase between 1975 and 2000 was primarily caused by an increase in papillary thyroid cancer, particularly over the most recent decade. The incidence of follicular thyroid cancer also increased while the incidence of anaplastic and medullary thyroid cancer did not change significantly. Mortality from thyroid cancer fell progressively between 1960 and 2002. EASR for females decreased from 1.05 to 0.28 (P < 0.001) and in males from 0.73 to 0.34 (P < 0.001). For both sexes, in general, survival at 1-, 5- and 10-year follow-up intervals from diagnosis improved steadily over the study period. In both females and males, survival from thyroid cancer was better if the diagnosis was made under the age of 50 years.

Conclusions: Thyroid cancer incidence has increased in Scotland over the past 40 years. This is accompanied by a change in the distribution of histological type with a particular increase in papillary carcinoma. The reasons for this may relate partly to changes in clinical practice and histological criteria. Falling mortality in the face of increasing incidence reflects improvements in survival, which should improve further with the introduction and implementation of standardized treatment protocols.