[Time trends in the geographic variation of thyroid cancer incidence by tumor size from 1983 to 2000 in France].

BACKGROUND: The aim of this investigation was to study geographic time trends of thyroid cancer incidence according to tumor size in France, 1983 to 2000.

METHODS: Incidence data were provided from six French registries over the period 1983-2000 covering seven administrative districts. Five tumor size groups were distinguished: < 10mm, 10-20mm, 20-40mm, > 40mm and unknown size. Papillary cancers diagnosed in women were analyzed according to tumor size in each geographic area. World age standardized rates were calculated and annual percent change rates were estimated for each tumor size group in each geographic area. Loglinear Poisson regression models were used to study geographic discrepancies in time trends incidences.

RESULTS: The six French registries included 2222 papillary thyroid cancers in women between 1983 et 2000. Thyroid cancer incidence was increasing in the six geographic areas. Geographical variations in time trends incidence between registries reflected geographical variations in time trends incidence of small sized tumors (less than 10mm).

CONCLUSION: Wide geographic variations in thyroid cancer incidence were noticed for small size tumors, which may be correlated with geographic variations in medical practices.