Thyroid Cancer Incidence Patterns in Algeria by Demographic and Tumor Characteristics: 1993-2013

  • Background : The incidence of thyroid cancer (TC) has dramatically increased over the last three decades in several countries, and the reasons of this increase are still debated. We carried out a population-based investigation to determine incidence rates (IRs) and temporal trends of TC in Algeria, and to determine the impact of the major histologic subtypes on these trends during the 1993-2013 period.

    Methods : Retrospective cohort study of patients with TC. Age-adjusted (to the world population) IRs were calculated by sex and histology. Trends in IRs were assessed by calculating the estimated annual percentage change (EAPC). The joinpoint regression analysis was used to identify time points (in calendar years) where changes had possibly occurred.

    Results : During the study period, TC IRs increased from 4,5 per 100 000 in 1993-1997 to 12,6 per 100 000 in 2008-2013 in women, and from 0,5 per 100 000 in 1993-1997 to 2,0 per 100 000 in 2008-2013 in men. (Overall EAPC: +3.8% ; p <0.05). A significant increase in incidence of papillary carcinomas (EAPC: +6.02% ; p <0.05), and carcinomas ?20 mm (EAPC: +7.30% ; p<0.05) was observed, and was more pronounced for women <45 years (EAPC: +8,11% ; p <0.05) compared with women ?45 years (EAPC: +5,58% ; p <0.05), while incidence of the follicular subtype significantly decreased (EAPC : -3.78% ; p<0,05).

    Conclusions : The significant change toward more extensive thyroid surgery for multinodular goiter and solitary cold nodules may have led to overdiagnosis. However, the correction of iodine deficiency introduced in Algeria in the 1970s may also have played a determinant role in the observed trends. 

 

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