Papillary thyroid cancer incidence in the volcanic area of Sicily.
BACKGROUND
The steadily increasing incidence of thyroid cancer has been attributed mostly to more sensitive thyroid nodule screening. However, various environmental factors, such as those associated with volcanic areas, cannot be excluded as risk factors. We evaluated thyroid cancer incidence in Sicily, which has a homogenous population and a province (Catania) that includes the Mt Etna volcanic area.


METHODS
In a register-based epidemiological survey, we collected all incident thyroid cancers in Sicily from January 1, 2002, through December 31, 2004. The age-standardized incidence rate for the world population (ASR(w)) was calculated and expressed as the number of thyroid cancer diagnoses per 100 000 residents per year. The association of thyroid cancer incidence rate with sex, age, tumor histotype, and various environmental factors was evaluated by modeling the variation of the ASR(w). All statistical tests were two-sided.


RESULTS
In 2002-2004, 1950 incident thyroid cancers were identified in Sicily (among women, ASR(w) = 17.8, 95% confidence interval [CI] = 16.9 to 18.7; and among men, ASR(w) = 3.7, 95% CI = 3.3 to 4.1). Although the percentage of thyroid cancers that were microcarcinomas (ie, < or = 10 mm) and ratio of men to women with thyroid cancer were similar in all nine Sicilian provinces, thyroid cancer incidence was statistically significantly higher in the province of Catania (among women, ASR(w) = 31.7, 95% CI = 29.1 to 34.3; and among men, ASR(w) = 6.4, 95% CI = 5.2 to 7.5) than in the rest of Sicily (among women, ASR(w) = 14.1, 95% CI = 13.2 to 15.0; and among men, ASR(w) = 3.0, 95% CI = 2.6 to 3.4) (all P values < .001). Incidence of papillary, but not follicular or medullary, cancers was statistically significantly increased in Catania province, and papillary tumors from patients in Catania more frequently carried the BRAF V600E gene mutation (55 [52%] of 106 tumors) than tumors from patients elsewhere in Sicily (68 [33%] of 205 tumors) (relative risk = 1.7, 95% CI = 1.0 to 2.8, P = .02). Cancer incidence was statistically significantly lower in rural areas than in urban areas of Sicily (P = .003). No association with mild iodine deficiency or industrial installations was found. Levels of many elements (including boron, iron, manganese, and vanadium) in the drinking water of Catania province often exceeded maximum admissible concentrations, in contrast to water in the rest of Sicily.


CONCLUSIONS
Residents of Catania province with its volcanic region appear to have a higher incidence of papillary thyroid cancer than elsewhere in Sicily.
Pellegriti
Gabriella
G
Endocrinology Division, Department of Internal and Specialistic Medicine, University of Catania Medical School, Garibaldi-Nesima Hospital, Catania, Italy. gabriellapellegriti@hotmail.com
De Vathaire
Florent
F
Scollo
Claudia
C
Attard
Marco
M
Giordano
Carla
C
Arena
Salvatore
S
Dardanoni
Gabriella
G
Frasca
Francesco
F
Malandrino
Pasqualino
P
Vermiglio
Francesco
F
Previtera
Domenico Massimo
DM
D'Azzò
Girolamo
G
Trimarchi
Francesco
F
Vigneri
Riccardo
R
D018263:Adenocarcinoma, Follicular / Q000453:epidemiology / Q000209:etiology; D000293:Adolescent; D000328:Adult; D017677:Age Distribution; D000368:Aged; D000369:Aged, 80 and over; D018276:Carcinoma, Medullary / Q000453:epidemiology / Q000209:etiology; D002291:Carcinoma, Papillary / Q000453:epidemiology* / Q000209:etiology* / Q000235:genetics; D004781:Environmental Exposure / Q000009:adverse effects*; D005260:Female; D006801:Humans; D015994:Incidence; D008297:Male; D008875:Middle Aged; D009154:Mutation; D048493:Proto-Oncogene Proteins B-raf / Q000235:genetics; D012042:Registries; D018570:Risk Assessment; D012307:Risk Factors; D017678:Sex Distribution; D012802:Sicily / Q000453:epidemiology; D013964:Thyroid Neoplasms / Q000453:epidemiology* / Q000209:etiology* / Q000235:genetics; D018707:Volcanic Eruptions / Q000009:adverse effects*; D055815:Young Adult
C482119:BRAF protein, human; D048493:Proto-Oncogene Proteins B-raf