Racial/ethnic differences in thyroid cancer incidence in the United States, 2007-2014

Small tumor diagnostic tools including ultrasound-guided fine needle aspiration (FNA) and computed tomography (CT) could be causing rising and racially/ethnically different thyroid cancer incidence rates due to variable overdiagnosis of indolent tumors. Papillary tumors and <40 mm tumors are most likely to be overdiagnosed as indolent tumors by FNA and CT.

Age-adjusted incidence rates (AAIRs) for the years 2007-2014 were calculated for race/ethnicity (white, Hispanic, Asian, African American, Native American) by patient/tumor characteristics for microscopically confirmed malignant thyroid cancer cases in the Surveillance, Epidemiology, and End Results Program 18 database (SEER 18; N = 93,607). Multivariate analysis determined cancer patients' odds ratios of diagnosis with papillary thyroid carcinoma (vs other histologies) and tumors <40 mm (vs ≥40 mm).

For both males and females, there were statistically significant differences in incidence rates between race/ethnicity, with whites having the highest AAIRs and African Americans the lowest AAIRs. Among thyroid cancer patients, tumor size and histology differed significantly by race and insurance coverage after controlling for age, sex, stage, and tumor sequence. Non-whites with thyroid cancer (vs whites) were less associated with small tumors (odds ratio [OR], 0.51-0.79; P < .0001). Medicaid and uninsured patients with thyroid cancer were less associated with tumors <40 mm (OR, 0.55-0.71; 95% confidence interval [CI], 0.49-0.76) and papillary carcinoma (OR, 0.86; 95% CI, 0.80-0.93).

The diagnosis of small tumors is occurring at greater rates in whites (vs non-whites) and insured (vs Medicaid and uninsured) patients; consequently, these groups may be vulnerable to unnecessary tests and treatments or potentially aided by early detection. Guidelines that define postdetection interventions may be needed to limit the overtreatment of indolent and small papillary carcinomas. Cancer 2018;124:1483-91. © 2018 American Cancer Society.