Incidence of thyroid cancer in Puerto Rico and the US by racial/ethnic group, 2011-2015.

Background: Puerto Rico has the highest incidence rate of thyroid cancer (TC) in the Americas and the third highest rate worldwide. The purpose of this study was to compare the burden of TC between the population of PR and United States (US) non-Hispanic Whites (NHW), non-Hispanic Blacks (NHB), and US Hispanics (USH) during the period 2011-2015.
Methods: TC data for the period 2011-2015 was obtained from the Puerto Rico Central Cancer Registry (PRCCR) and the Surveillance Epidemiology and Ends Results Program (SEER) 18 Registries Research Data. TC was categorized in: papillary carcinoma (PTC), and other TC histologic types. Data was analyzed by sex, age groups, and histologic type. Racial/ethnic differences by sex, age, and histologic types were assessed using the Standardized Rate Ratio (SRR) and its 95% CI.
Results: During the period 2011-2015 there were 5175 and 65,528 cases of TC diagnosed in PR and the US, respectively. The overall age-adjusted incidence rate of PTC was almost two-fold higher in PR than in the US (25.8/100,000 vs. 12.9/100,000). Among PR women, the incidence rate of PTC was 40.0/100,000 compared to 19.4/100,000 in US. PR women had 83% increased risk of being diagnosed with PTC than NHW women, a 2.25-fold increased risk than USH, and 3.45-fold increased risk than NHB women. For men, PR had 34% increased risk of being diagnosed with PTC than NHW men, 2.2-fold increased risk than USH men, and 3.2-fold higher risk than in NHB men.
Conclusion: Further research is needed to understand this disparity in the island. This research should address the extent of overdiagnosis in PR, the role of health insurance status and insurance type, characteristics of the healthcare delivery system as well as the role of patient and environmental factors.