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.
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 (ASRw) 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 ASRw. All statistical tests were two-sided.
In 2002–2004, 1950 incident thyroid cancers were identified in Sicily (among women, ASRw = 17.8, 95% confidence interval [CI] = 16.9 to 18.7; and among men, ASRw = 3.7, 95% CI = 3.3 to 4.1). Although the percentage of thyroid cancers that were microcarcinomas (ie, ≤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, ASRw = 31.7, 95% CI = 29.1 to 34.3; and among men, ASRw = 6.4, 95% CI = 5.2 to 7.5) than in the rest of Sicily (among women, ASRw = 14.1, 95% CI = 13.2 to 15.0; and among men, ASRw = 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.
Residents of Catania province with its volcanic region appear to have a higher incidence of papillary thyroid cancer than elsewhere in Sicily.
Since the 1980s, Spain experienced two decades of sharply increasing breast cancer incidence. Declines in breast cancer incidence have recently been reported in many developed countries. We examined whether a similar downturn might have taken place in Spain in recent years.
Cases of invasive female breast cancer were drawn from all population-based Spanish cancer registries that had at least 10 years of uninterrupted registration over the period 1980–2004. Overall and age-specific changes in incidence rates were evaluated using change-point Poisson models, which allow for accurate detection and estimation of trend changes. All statistical tests were two-sided.
A total of 80 453 incident cases of invasive breast cancer were identified. Overall age- and registry-adjusted incidence rates rose by 2.9% (95% confidence interval [CI] = 2.7% to 3.1%) annually during the 1980s and 1990s; there was a statistically significant change in this trend in 2001 (95% CI = 1998 to 2004; P value for the existence of a change point <.001), after which incidence declined annually by 3.0% (95% CI = 1.8% to 4.1%). This trend differed by age group: There was a steady increase in incidence for women younger than 45 years, an abrupt downturn in 2001 for women aged 45–64 years, and a gradual leveling off in 1995 for women aged 65 years or older. Separate analyses for registries that had at least 15 years of uninterrupted registration detected a statistically significant interruption of the previous upward trend in breast cancer incidence in provinces that had aggressive breast cancer screening programs and high screening participation rates, including Navarra (change point = 1991, P < .001), Granada (change point = 2002, P = .003), Bizkaia (change point = 1998, P < .001), Gipuzkoa (change point = 1998, P = .001), and Araba (change point = 1997, P = .002).
The recent downturn in breast cancer incidence among Spanish women older than 45 years is best explained by a period effect linked to screening saturation.