Decreasing tumor size of thyroid cancer in Germany: institutional experience 1995-2009.

OBJECTIVE: Decreasing tumor size in a population over time is widely interpreted as a measure of effectiveness of cancer screening programs. Nonetheless, thyroid cancer size is rarely analyzed as a function of time. This study aimed to explore secular trends of thyroid cancer diameter in Germany.
DESIGN: Retrospective analysis of 1644 thyroid cancer patients from a large referral center for thyroid cancer (1995-2009).
METHODS: Calculation of largest tumor diameters for each type of cancer as a function of time periods and birth cohorts.
RESULTS: Over the past 25 years, subdivided into 5-year periods by year of thyroidectomy (1985-1989; 1990-1994; 1995-1999; 2000-2004; 2005-2009), tumor diameters diminished from 25 to 16 mm (P=0.025) for medullary thyroid cancer and from 28 to 18 mm (P=0.017) for papillary thyroid cancer. This reduction was greater for hereditary medullary thyroid cancer (from 27 to 11 mm; P=0.088) than sporadic medullary thyroid cancer (from 23 to 19 mm; P=0.11). No decline was observed for follicular thyroid cancer (means of 45 to 42 mm; P=0.52). From the first (1921-1940) to the most recent birth cohort (1981-2000), tumor size fell from 22 to 10 mm (P<0.001) for medullary thyroid cancer, from 24 to 22 mm (P<0.001) for papillary thyroid cancer, and from 49 to 38 mm (P=0.011) for follicular thyroid cancer. The reduction of medullary thyroid cancers affected exclusively patients with hereditary disease (from 20 to 7 mm; P<0.001).
CONCLUSION: The consistency and robustness of these data signify powerful secular trends toward smaller papillary, follicular, and medullary thyroid cancers. The causes and consequences of these trends warrant further investigation.