Differentiated thyroid cancer in Greece: 1963-2000. Relation to demographic and environmental factors.

Thyroid cancer (TC) is a relatively rare neoplasia, accounting for 0.35%-0.38% of total deaths due to cancer in Greece. Environmental/nutritional factors are considered to play a role in its pathogenesis. The aim of this retrospective review of patients' histories from three of the largest specialized centers in southern Greece, from 1963 to 2000, was to assess associations of differentiated TC (DTC) with demographic and environmental factors. The total number of DTC cases was 610 (119 men or 19.5%, and 491 women or 80.5%), of which 442 cases (72%) were papillary DTCs (pure papillary type: 54.5% and mixed papillary-follicular type: 45.5%), 90 cases (15%) were of the pure follicular type, while 78 cases (13%) were classified as suspicious lesions, requiring follow-up, but not definitively carcinomas. The mean age (+/-SD) at diagnosis for all groups was 42.3+/-1.3 years. Fifty percent of the patients were living in Athens at the time of diagnosis. The diagnosis was delayed in patients living in villages compared to those living in cities (mean age +/-SD): 43.7+/-14.1 years and 40.9+/-13.8 years, respectively; p<0.05, t-test). Patients who were born in iodine-sufficient areas (n=162/193, 84%; X(2)=5.09, P=0.02) had papillary carcinoma more frequently compared to patients who were born in previously iodine-deficient areas (n=159/214, 74%). During the observation period (1963-2000) there appeared to be three different trends in the incidence of newly diagnosed cases: a random variation during the first nine years and a steady increase during the second two decades (starting before the Chernobyl nuclear accident) followed by a significant decline during the last few years. We suggest that the observed variations in the incidence of DTC could be related to the availability of diagnostic tools as well as to increased awareness.