"Thyroid cancer incidence is leveling off in the United States. Our analysis, however, shows that the trend of deceleration mainly occurred in non-Hispanic Whites and in older populations, whereas the rate of thyroid cancer continuously increased among the young and the Hispanic and black populations," said lead author Anupam Kotwal, M.B.B.S., clinical fellow in the Division of Endocrinology, Diabetes, Metabolism and Nutrition at Mayo Clinic in Rochester, Minn.
"Our findings are important because they suggest disparity in thyroid cancer diagnosis with possible implications in disease-specific outcomes as well as societal and economic costs," he added.
To examine the trend of thyroid cancer in different age and gender subgroups, Kotwal and colleagues reviewed age-adjusted incidence, including average percent change in incidence and trends in age-adjusted rates from the National Cancer Institute Surveillance, Epidemiology, and End Results (SEER 18) program. They analyzed data from the years 2000 through 2013 using the publicly available online interactive tool (SEER*Explorer).
From 2000 to 2013, thyroid cancer incidence increased from 7.4 to 14.5 cases per 100,000 people, with an average change of 6.7 percent from 2000 through 2009 and 2.4 percent from 2010 through 2013.
In Hispanics and African Americans, thyroid cancer incidence has continuously increased, with an average change of 4.7 percent and 5.1 percent respectively, while for non-Hispanic Whites, the average change decelerated from 7.1 percent before 2009 to 2.2 percent after 2009.
Stratified by age group, thyroid cancer continued to accelerate at an unchanged rate only among people 20 years of age and below. Among those 75 years of age and above, though, the rising incidence stabilized after 2009, with an average change of 1 percent.
Females and males showed similar deceleration in their overall rates after 2009, with average changes of 2.3 percent and 2.8 percent, respectively.
When subgroups were combined based on their association with acceleration or deceleration rates, the group with the highest average percent change without any evidence of deceleration was Hispanic females between the ages of 20 and 49 years.
"These findings are consistent with recent reports demonstrating that thyroid cancer is the second most common cancer among Hispanic females, female adolescents and young adults. Drivers for these variations in thyroid cancer trends are unknown and require further investigation," Kotwal said.
"Future analysis will demonstrate if this change in thyroid cancer incidence persists. Whether this increase in incidence is due to more testing (e.g., thyroid ultrasound) or truly represents a higher predilection of these patient groups for thyroid cancer will need further investigation," he added.
Juan P. Brito, M.B.B.S., assistant professor of medicine at the Mayo Clinic in Rochester, Minn. was senior author of the study with Kotwal. The study received no external funding. # # #
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