The effects of race and ethnicity on thyroid cancer incidence

The incidence of thyroid cancer has increased over the past 30 years. Thyroid cancer is less common in blacks than in persons of white descent, and it has been most common in Asians/Pacific Islanders until recently.

To determine whether the incidence of thyroid cancer is increasing at disproportionate rates for different races and ethnicities.

Retrospective review. Study participants were individuals with thyroid cancer in the US National Cancer Institute's Surveillance, Epidemiology, and End Results (SEER) 13 database from 1992 through 2010. The SEER 13 registry consists of records from Atlanta (Georgia), Connecticut, Detroit (Michigan), Hawaii, Iowa, New Mexico, San Francisco-Oakland (California), Seattle-Puget Sound (Washington), Utah, Los Angeles (California), San Jose-Monterey (California), rural Georgia, and the Alaska Native Tumor Registry.

The SEER*Stat Joinpoint Regression Program was used to determine the average annual percentage change in thyroid cancer incidence for different races and ethnicities from 1992 through 2010. Trends in thyroid cancer incidence were compared between groups using comparability testing.

During the study period, the average annual percentage change for thyroid cancer was 5.3% (95% CI, 4.8%-5.7%) per year. Stratification of the study population by race revealed that whites experienced the largest increase in age-adjusted thyroid cancer incidence (5.6% per year), followed by blacks (4.8% per year), American Indian/Alaskan natives (3.2% per year), and Asians/Pacific Islanders (2.3% per year). Joinpoint regression comparability testing showed that the increase in disease incidence was not significantly different between whites and blacks (P = .25). However, the increase in incidence for Asians/Pacific Islanders was significantly lower than that for whites and blacks (P < .05). Stratification of the study population by ethnicity revealed that non-Hispanics experienced a larger increase in incidence (5.5% per year) than Hispanics (3.3% per year).

The incidence of thyroid cancer continues to increase in all races and ethnicities. No significant difference was observed between the increase in incidence for whites and blacks. However, the increase in incidence for non-Hispanics was significantly larger than that for Hispanics. The increase in incidence of thyroid cancer was greater in whites than in Asians/Pacific Islanders, so whites now have a higher incidence of thyroid cancer than persons of Asian/Pacific Islander descent.