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Figure 1.
1992-2010 Thyroid Cancer Average Annual Percentage Change by Race
1992-2010 Thyroid Cancer Average Annual Percentage Change by Race

The thyroid cancer average annual percentage change is higher in whites than in blacks and Asians/Pacific Islanders for both men and women. Limit lines indicate 95% CIs.

Figure 2.
1992-2010 Thyroid Cancer Average Annual Percentage Change by Ethnicity
1992-2010 Thyroid Cancer Average Annual Percentage Change by Ethnicity

The thyroid cancer average annual percentage change is higher in non-Hispanics than in Hispanics for both men and women. Limit lines indicate 95% CIs.

Figure 3.
Thyroid Cancer Incidence vs Year by Race
Thyroid Cancer Incidence vs Year by Race

In 2002, the thyroid cancer incidence in whites surpassed that in Asians/Pacific Islanders.

Table 1.  
Thyroid Cancer Incidence per 100 000 From 2007 to 2011a
Thyroid Cancer Incidence per 100 000 From 2007 to 2011a
Table 2.  
Average Annual Percentage Change in Age-Adjusted Thyroid Cancer Incidence
Average Annual Percentage Change in Age-Adjusted Thyroid Cancer Incidence
1.
National Cancer Institute. Thyroid cancer.http://www.cancer.gov/cancertopics/types/thyroid. Accessed June 14, 2014.
2.
Davies  L, Welch  HG.  Increasing incidence of thyroid cancer in the United States, 1973-2002. JAMA. 2006;295(18):2164-2167.
PubMedArticle
3.
Enewold  L, Zhu  K, Ron  E,  et al.  Rising thyroid cancer incidence in the United States by demographic and tumor characteristics, 1980-2005. Cancer Epidemiol Biomarkers Prev. 2009;18(3):784-791.
PubMedArticle
4.
Lubitz  CC, Kong  CY, McMahon  PM,  et al.  Annual financial impact of well-differentiated thyroid cancer care in the United States. Cancer. 2014;120(9):1345-1352.
PubMedArticle
5.
Ward  E, Jemal  A, Cokkinides  V,  et al.  Cancer disparities by race/ethnicity and socioeconomic status. CA Cancer J Clin. 2004;54(2):78-93.
PubMedArticle
6.
Bach  PB, Schrag  D, Brawley  OW, Galaznik  A, Yakren  S, Begg  CB.  Survival of blacks and whites after a cancer diagnosis. JAMA. 2002;287(16):2106-2113.
PubMedArticle
7.
Miller  BA, Kolonel  LN, Bernstein  L,  et al, eds. Racial/Ethnic Patterns of Cancer in the United States 1988-1992. Bethesda, MD: National Cancer Institute; 1996. National Institutes of Health publication 96-4104.
8.
Morris  LG, Sikora  AG, Myssiorek  D, DeLacure  MD.  The basis of racial differences in the incidence of thyroid cancer. Ann Surg Oncol. 2008;15(4):1169-1176.
PubMedArticle
9.
Hodgson  NC, Button  J, Solorzano  CC.  Thyroid cancer. Ann Surg Oncol. 2004;11(12):1093-1097.
PubMedArticle
10.
Hollenbeak  CS, Wang  L, Schneider  P, Goldenberg  D.  Outcomes of thyroid cancer in African Americans. Ethn Dis. 2011;21(2):210-215.
PubMed
11.
Kent  WD, Hall  SF, Isotalo  PA, Houlden  RL, George  RL, Groome  PA.  Increased incidence of differentiated thyroid carcinoma and detection of subclinical disease. CMAJ. 2007;177(11):1357-1361.
PubMedArticle
12.
Davies  L, Ouellette  M, Hunter  M, Welch  HG.  The increasing incidence of small thyroid cancers. Laryngoscope. 2010;120(12):2446-2451.
PubMedArticle
13.
Brown  SR, Lee  S, Brown  TA, Waddell  BE.  Effect of race on thyroid cancer care in an equal access healthcare system. Am J Surg. 2010;199(5):685-689.
PubMedArticle
14.
Cramer  JD, Fu  P, Harth  KC, Margevicius  S, Wilhelm  SM.  Analysis of the rising incidence of thyroid cancer using the Surveillance, Epidemiology, and End Results national cancer data registry. Surgery. 2010;148(6):1147-1152.
PubMedArticle
15.
Gursoy  A.  Rising thyroid cancer incidence in the world might be related to insulin resistance. Med Hypotheses. 2010;74(1):35-36.
PubMedArticle
16.
Li  N, Du  XL, Reitzel  LR, Xu  L, Sturgis  EM.  Impact of enhanced detection on the increase in thyroid cancer incidence in the United States. Thyroid. 2013;23(1):103-110.
PubMedArticle
17.
Hardy  D, Liu  CC, Xia  R,  et al.  Racial disparities and treatment trends in a large cohort of elderly black and white patients with nonsmall cell lung cancer. Cancer. 2009;115(10):2199-2211.
PubMedArticle
18.
Freedman  RA, He  Y, Winer  EP, Keating  NL.  Trends in racial and age disparities in definitive local therapy of early-stage breast cancer. J Clin Oncol. 2009;27(5):713-719.
PubMedArticle
19.
Albain  KS, Unger  JM, Crowley  JJ, Coltman  CA  Jr, Hershman  DL.  Racial disparities in cancer survival among randomized clinical trials patients of the Southwest Oncology Group. J Natl Cancer Inst. 2009;101(14):984-992.
PubMedArticle
20.
Harper  S, Lynch  J. Methods for Measuring Cancer Disparities: Using Data Relevant to Healthy People 2010 Cancer-Related Objectives. Bethesda, MD: National Cancer Institute; 2005. National Cancer Institute Cancer Surveillance Monograph Series 6. National Institutes of Health publication 05-5777.
21.
Blackwell  DL, Lucas  JW, Clarke  TC.  Summary health statistics for U.S. adults: national health interview survey, 2012. Vital Health Stat 10. 2014;(260):1-161.
PubMed
22.
Aschebrook-Kilfoy  B, Kaplan  EL, Chiu  BC, Angelos  P, Grogan  RH.  The acceleration in papillary thyroid cancer incidence rates is similar among racial and ethnic groups in the United States. Ann Surg Oncol. 2013;20(8):2746-2753.
PubMedArticle
23.
Nikiforov  YE.  Radiation-induced thyroid cancer. Endocr Pathol. 2006;17(4):307-317.
PubMedArticle
24.
Feldt-Rasmussen  U.  Iodine and cancer. Thyroid. 2001;11(5):483-486.
PubMedArticle
25.
Dijkstra  B, Prichard  RS, Lee  A,  et al.  Changing patterns of thyroid carcinoma. Ir J Med Sci. 2007;176(2):87-90.
PubMedArticle
26.
Horn-Ross  PL, Canchola  AJ, Ma  H, Reynolds  P, Bernstein  L.  Hormonal factors and the risk of papillary thyroid cancer in the California Teachers Study cohort. Cancer Epidemiol Biomarkers Prev. 2011;20(8):1751-1759.
PubMedArticle
27.
Peterson  E, De  P, Nuttall  R.  BMI, diet and female reproductive factors as risks for thyroid cancer. PLoS One. 2012;7(1):e29177. doi:10.1371/journal.pone.0029177.
PubMedArticle
28.
Xu  L, Port  M, Landi  S,  et al.  Obesity and the risk of papillary thyroid cancer. Thyroid. 2014;24(6):966-974.
PubMedArticle
29.
American Thyroid Association. Professional guidelines. http://www.thyroid.org/thyroid-guidelines/. Accessed December 23, 2014.
Original Investigation
April 2015

The Effects of Race and Ethnicity on Thyroid Cancer Incidence

Author Affiliations
  • 1Division of Otolaryngology–Head and Neck Surgery, Department of Surgery, College of Medicine, The Pennsylvania State University, Hershey
  • 2Division of Outcomes Research and Quality, Department of Surgery, College of Medicine, The Pennsylvania State University, Hershey
JAMA Otolaryngol Head Neck Surg. 2015;141(4):319-323. doi:10.1001/jamaoto.2014.3740
Abstract

Importance  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.

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

Design, Setting, and Participants  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.

Main Outcomes and Measures  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.

Results  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).

Conclusions and Relevance  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.

Introduction

Thyroid cancer, with an estimated incidence of 62 980 cases per year in the United States, is the most common endocrine cancer.1 Per 100 000, thyroid cancer in the United States has increased from an incidence in 1973 of 3.6 cases to an incidence in 2002 of 8.7 cases.2 Most of the increase is owing to papillary thyroid cancer, which is associated with a 95% 30-year survival rate.2,3 Despite its favorable long-term survival, thyroid cancer still poses significant clinical and economic burdens.4

Racial disparities are recognized in many different types of cancer. The prevalence of most cancers, including colorectal, lung, prostate, gastric, and head and neck, is higher among black populations than among persons of white descent, and blacks are more likely to die of their cancer.5,6 However, thyroid cancer is half as common in blacks as in whites.7 Historically, thyroid cancer incidence is highest in whites, followed by Asians/Pacific Islanders, American Indian/Alaskan natives, and blacks. Thyroid cancer incidence is higher in non-Hispanic men and women than in Hispanic men and women (Table 1).1

Our aim in this study was to compare the change in thyroid cancer incidence in whites, blacks, Asians/Pacific Islanders, and American Indian/Alaskan natives and in Hispanics and non-Hispanics. The study period was from 1992 through 2010.

Methods

This study was deemed exempt from review by the Penn State College of Medicine institutional review board. The National Cancer Institute’s Surveillance, Epidemiology, and End Results (SEER) database (http://seer.cancer.gov/) was used to determine the increase in incidence of thyroid cancer in this retrospective review. The SEER database is a population-based publicly available data set from a government agency that has been gathering data since 1973. Data are contributed by individual registries across the United States.

Many existing studies base their assumptions and conclusions on data from 1973 onward.2,8,9 However, detection of thyroid cancer greatly improved with the introduction of ultrasonography-guided fine-needle aspiration biopsies in the 1980s and 1990s.10 Therefore, data after 1992 more closely reflect the current state of thyroid cancer in the United States; for this reason, SEER data from 1992 through 2010 were used for this study. In particular, SEER 13 was selected because it has more racial categories than previous SEER data sets. SEER 13 has 4 different categories for race (white, black, Asian/Pacific Islander, and American Indian/Alaskan native) and 2 categories for ethnicity (Hispanic and non-Hispanic). Therefore, individuals of white race are also either Hispanic or non-Hispanic, individuals of black race are also either Hispanic or non-Hispanic, and so forth. 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 software version 8.0.4 Joinpoint Regression Program (National Cancer Institute) was used to determine the average annual percentage change (AAPC) in incidence for the thyroid cancer population described by SEER 13 data from 1992 through 2010. The AAPC in thyroid cancer incidence was calculated for each race and ethnicity over the entire study period and over the following 4 specified periods to simplify the comparison: 1992 through 1995, 1996 through 2000, 2001 through 2005, and 2006 through 2010. Joinpoint regression comparability testing for parallelism in annual percentage change in thyroid cancer incidence was conducted to compare trends over the entire study period for each race and ethnicity stratified by sex.

An AAPC can be calculated as a weighted average of the slope of the joinpoint regression curve over a fixed period (an interval with fixed join points). Therefore, the AAPC can be used to compare changes in cancer incidence between groups over specified intervals. Join point enables comparability testing for parallelism to determine whether the annual percentage change regression mean functions are parallel. If the P value is less than .05, then the null hypothesis that the regression mean functions are parallel is rejected.

Results

Table 2 lists the AAPC in age-adjusted thyroid cancer incidence by race, ethnicity, and sex. To simplify the comparison of trends in incidence, the AAPCs were calculated over the following 4 periods: 1992 through 1995, 1996 through 2000, 2001 through 2005, and 2006 through 2010. During the study period (1992-2010), the AAPC for thyroid cancer in all races and ethnicities 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 during the study period (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) (Figure 1). 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) (Figure 2). Whites and blacks experienced statistically similar increases in AAPCs, and trend analysis failed to reject parallelism between the groups (P = .25). The AAPCs for white and black women were also similar at 6.1% per year for white women and 5.9% per year for black women, with no significant difference in trends (P = .35).

The AAPC for Asians/Pacific Islanders (2.3% per year) was lower than that for whites (5.6% per year) (P < .05). Furthermore, the incidence of thyroid cancer in whites surpassed that of Asians/Pacific Islanders in 2002 (Figure 3). Thyroid cancer incidence is now highest in whites. In addition, the AAPC for Asians/Pacific Islanders (2.3% per year) was lower than that for blacks (4.8% per year) (P < .05).

The AAPC for American Indian/Alaskan natives (3.2% per year) was lower than that for whites (5.6% per year) (P < .05) and blacks (4.8% per year) (P < .05). However, the AAPC for American Indian/Alaskan natives (3.2% per year) was not significantly different from that for Asians/Pacific Islanders (2.3% per year) (P = .17).

Over the entire study period, the AAPCs for non-Hispanics and Hispanics were significantly different (P < .05). The AAPC for non-Hispanics was 5.5% per year, while the AAPC for Hispanics was 3.3% per year. Similarly, the AAPCs for non-Hispanic and Hispanic women were significantly different (P < .05), with an increase of 5.9% per year for non-Hispanic women and an increase of 3.7% per year for Hispanic women. Therefore, thyroid cancer incidence is increasing more quickly in non-Hispanic women than in Hispanic women.

Discussion

The increasing incidence of thyroid cancer across all racial and ethnic groups is an urgent public health concern, and various explanations have been suggested as the underlying cause. Some studies2,8,1113 have concluded that this increase in incidence is owing to an increase in the diagnosis of subclinical thyroid cancers, as opposed to an increase in the occurrence of thyroid cancer, because of an increased use of ultrasonography-guided fine-needle aspiration biopsies. These advanced diagnostic techniques enable detection of tumors that are 1 cm or smaller and would otherwise lie dormant and go undetected.10 The findings of other studies3,1416 suggest that the increase is owing to both an increase in the diagnosis of subclinical thyroid cancers and a true increase in thyroid cancer because of an increase in risk factors. Studies3,8,13,1720 have investigated the possibility that differences in thyroid cancer incidence between whites and blacks are owing to variations in socioeconomic status, resulting in differences in access to health care and detection and diagnosis of subclinical thyroid cancers. Assuming that whites have a higher socioeconomic status and more access to health care,21 they should have enhanced detection and diagnosis of subclinical thyroid cancer and a greater increase in thyroid cancer incidence than blacks. In addition, under the assumption that Asians/Pacific Islanders have more access to health care,21 they should also have a greater increase in thyroid cancer incidence than blacks. In the present study, no significant difference in increased thyroid cancer incidence was observed between whites and blacks, but the increased incidence for Asians/Pacific Islanders was significantly lower than that for blacks. This shift in thyroid cancer incidence among different races does not support the theory of access to care as the sole explanation.

In 2012, Hispanic men (48%) were less likely to have seen a physician in the past 6 months than non-Hispanic white men (63%) and non-Hispanic black men (58%).21 Hispanic women (68%) were also less likely to have seen a physician than non-Hispanic white women (76%) and non-Hispanic black women (75%).21 If differences in incidence were due to access to care, then non-Hispanics should have had a greater increase in thyroid cancer incidence than Hispanics. In fact, joinpoint regression comparability testing verified that the larger increase in incidence for non-Hispanics observed in this study was statistically significant. Therefore, differences in the incidence among Hispanics and non-Hispanics support the theory of access to care.

Historically, thyroid cancer incidence has been highest in Asians/Pacific Islanders. According to our study, the increase in thyroid cancer incidence was lowest in Asians/Pacific Islanders. Therefore, in 2002 the incidence of thyroid cancer in whites surpassed that in Asians/Pacific Islanders (Figure 3). Thyroid cancer incidence is now highest in whites.

Differential exposure to risk factors may also cause differences in the increase in thyroid cancer incidence by race and ethnicity. Risk factors for the development of thyroid cancer include female sex,22 exposure to ionizing radiation,23 and iodine deficiency or excess.24,25 Less understood risk factors include female hormones26 and obesity.27,28

Limitations of our study include the retrospective format and the use of somewhat rigid registry data. Therefore, the SEER registry does not provide us with important adjuvant information such as mode of diagnosis of thyroid nodules (examination vs sonography), body mass index (BMI) or body fat percentage, or previous thyroid surgery, so we could not comment on those differences by race and ethnicity. This information would help us explain the shift in race and ethnicity that we are seeing in this study. For example, mode of diagnosis may vary by different racial and ethnic groups because those with greater access to care would have a greater increase in the diagnosis of thyroid nodules by sonography. In addition, BMI and body fat percentage have a large role in the incidence of diagnosis of thyroid nodules by racial and ethnic groups. Populations with statistically lower BMIs may have thyroid nodules diagnosed more readily by physical examination, so the incidence of thyroid cancer may not increase to as great an extent in those populations. Also, populations with less access to care may have greater BMIs and a higher incidence of thyroid cancer. Finally, racial and ethnic groups who prophylactically have their thyroid glands removed after diagnosis of thyroid nodules would have a lower incidence of thyroid cancer. Therefore, we were unable to conclusively determine whether differences in thyroid cancer incidence by race and ethnicity are due to health care disparities (eg, access to ultrasonography-guided fine-needle aspiration biopsy or propensity for thyroid surgery for benign neoplasms) or other risk factors (eg, exposure to ionizing radiation or BMI and body fat percentage). In addition, our data set only includes information through 2010. The American Thyroid Association29 introduced revised thyroid cancer diagnosis protocols in 2009, so we were unable to evaluate the effects of those protocols on the rise in thyroid cancer incidence.

Conclusions

With the increased thyroid cancer incidence, a shift in incidence has occurred among different races and ethnicities. Differences in access to care among races and ethnicities are not fully understood, but they may have a role in the shift in incidence. Other contributing factors include sex, exposure to environmental risks, lack or excess of dietary risks, and obesity. Further investigation of the various risk factors in different racial and ethnic groups is needed.

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Article Information

Submitted for Publication: August 21, 2014; final revision received November 5, 2014; accepted December 9, 2014.

Corresponding Author: David Goldenberg, MD, Division of Otolaryngology–Head and Neck Surgery, Department of Surgery, College of Medicine, The Pennsylvania State University, 500 University Dr, Mail Code H091, Hershey, PA 17033-0850 (dgoldenberg@hmc.psu.edu).

Published Online: February 5, 2015. doi:10.1001/jamaoto.2014.3740.

Author Contributions: Drs Schubart and Goldenberg had full access to all the data in the study and take responsibility for the integrity of the data and the accuracy of the data analysis.

Study concept and design: Magreni, Schubart, Goldenberg.

Acquisition, analysis, or interpretation of data: All authors.

Drafting of the manuscript: Magreni, Bann.

Critical revision of the manuscript for important intellectual content: All authors.

Study supervision: Goldenberg.

Conflict of Interest Disclosures: None reported.

Funding/Support: This study was supported by grant F30 CA165774 from the National Institutes of Health (Dr Bann).

Role of the Funder/Sponsor: The funding source had no role in the design and conduct of the study; collection, management, analysis, and interpretation of the data; preparation, review, or approval of the manuscript; and decision to submit the manuscript for publication.

Previous Presentation: This study was presented at the 5th World Congress of the International Federation of Head and Neck Oncologic Societies and Annual Meeting of the American Head and Neck Society; July 27, 2014; New York, New York.

References
1.
National Cancer Institute. Thyroid cancer.http://www.cancer.gov/cancertopics/types/thyroid. Accessed June 14, 2014.
2.
Davies  L, Welch  HG.  Increasing incidence of thyroid cancer in the United States, 1973-2002. JAMA. 2006;295(18):2164-2167.
PubMedArticle
3.
Enewold  L, Zhu  K, Ron  E,  et al.  Rising thyroid cancer incidence in the United States by demographic and tumor characteristics, 1980-2005. Cancer Epidemiol Biomarkers Prev. 2009;18(3):784-791.
PubMedArticle
4.
Lubitz  CC, Kong  CY, McMahon  PM,  et al.  Annual financial impact of well-differentiated thyroid cancer care in the United States. Cancer. 2014;120(9):1345-1352.
PubMedArticle
5.
Ward  E, Jemal  A, Cokkinides  V,  et al.  Cancer disparities by race/ethnicity and socioeconomic status. CA Cancer J Clin. 2004;54(2):78-93.
PubMedArticle
6.
Bach  PB, Schrag  D, Brawley  OW, Galaznik  A, Yakren  S, Begg  CB.  Survival of blacks and whites after a cancer diagnosis. JAMA. 2002;287(16):2106-2113.
PubMedArticle
7.
Miller  BA, Kolonel  LN, Bernstein  L,  et al, eds. Racial/Ethnic Patterns of Cancer in the United States 1988-1992. Bethesda, MD: National Cancer Institute; 1996. National Institutes of Health publication 96-4104.
8.
Morris  LG, Sikora  AG, Myssiorek  D, DeLacure  MD.  The basis of racial differences in the incidence of thyroid cancer. Ann Surg Oncol. 2008;15(4):1169-1176.
PubMedArticle
9.
Hodgson  NC, Button  J, Solorzano  CC.  Thyroid cancer. Ann Surg Oncol. 2004;11(12):1093-1097.
PubMedArticle
10.
Hollenbeak  CS, Wang  L, Schneider  P, Goldenberg  D.  Outcomes of thyroid cancer in African Americans. Ethn Dis. 2011;21(2):210-215.
PubMed
11.
Kent  WD, Hall  SF, Isotalo  PA, Houlden  RL, George  RL, Groome  PA.  Increased incidence of differentiated thyroid carcinoma and detection of subclinical disease. CMAJ. 2007;177(11):1357-1361.
PubMedArticle
12.
Davies  L, Ouellette  M, Hunter  M, Welch  HG.  The increasing incidence of small thyroid cancers. Laryngoscope. 2010;120(12):2446-2451.
PubMedArticle
13.
Brown  SR, Lee  S, Brown  TA, Waddell  BE.  Effect of race on thyroid cancer care in an equal access healthcare system. Am J Surg. 2010;199(5):685-689.
PubMedArticle
14.
Cramer  JD, Fu  P, Harth  KC, Margevicius  S, Wilhelm  SM.  Analysis of the rising incidence of thyroid cancer using the Surveillance, Epidemiology, and End Results national cancer data registry. Surgery. 2010;148(6):1147-1152.
PubMedArticle
15.
Gursoy  A.  Rising thyroid cancer incidence in the world might be related to insulin resistance. Med Hypotheses. 2010;74(1):35-36.
PubMedArticle
16.
Li  N, Du  XL, Reitzel  LR, Xu  L, Sturgis  EM.  Impact of enhanced detection on the increase in thyroid cancer incidence in the United States. Thyroid. 2013;23(1):103-110.
PubMedArticle
17.
Hardy  D, Liu  CC, Xia  R,  et al.  Racial disparities and treatment trends in a large cohort of elderly black and white patients with nonsmall cell lung cancer. Cancer. 2009;115(10):2199-2211.
PubMedArticle
18.
Freedman  RA, He  Y, Winer  EP, Keating  NL.  Trends in racial and age disparities in definitive local therapy of early-stage breast cancer. J Clin Oncol. 2009;27(5):713-719.
PubMedArticle
19.
Albain  KS, Unger  JM, Crowley  JJ, Coltman  CA  Jr, Hershman  DL.  Racial disparities in cancer survival among randomized clinical trials patients of the Southwest Oncology Group. J Natl Cancer Inst. 2009;101(14):984-992.
PubMedArticle
20.
Harper  S, Lynch  J. Methods for Measuring Cancer Disparities: Using Data Relevant to Healthy People 2010 Cancer-Related Objectives. Bethesda, MD: National Cancer Institute; 2005. National Cancer Institute Cancer Surveillance Monograph Series 6. National Institutes of Health publication 05-5777.
21.
Blackwell  DL, Lucas  JW, Clarke  TC.  Summary health statistics for U.S. adults: national health interview survey, 2012. Vital Health Stat 10. 2014;(260):1-161.
PubMed
22.
Aschebrook-Kilfoy  B, Kaplan  EL, Chiu  BC, Angelos  P, Grogan  RH.  The acceleration in papillary thyroid cancer incidence rates is similar among racial and ethnic groups in the United States. Ann Surg Oncol. 2013;20(8):2746-2753.
PubMedArticle
23.
Nikiforov  YE.  Radiation-induced thyroid cancer. Endocr Pathol. 2006;17(4):307-317.
PubMedArticle
24.
Feldt-Rasmussen  U.  Iodine and cancer. Thyroid. 2001;11(5):483-486.
PubMedArticle
25.
Dijkstra  B, Prichard  RS, Lee  A,  et al.  Changing patterns of thyroid carcinoma. Ir J Med Sci. 2007;176(2):87-90.
PubMedArticle
26.
Horn-Ross  PL, Canchola  AJ, Ma  H, Reynolds  P, Bernstein  L.  Hormonal factors and the risk of papillary thyroid cancer in the California Teachers Study cohort. Cancer Epidemiol Biomarkers Prev. 2011;20(8):1751-1759.
PubMedArticle
27.
Peterson  E, De  P, Nuttall  R.  BMI, diet and female reproductive factors as risks for thyroid cancer. PLoS One. 2012;7(1):e29177. doi:10.1371/journal.pone.0029177.
PubMedArticle
28.
Xu  L, Port  M, Landi  S,  et al.  Obesity and the risk of papillary thyroid cancer. Thyroid. 2014;24(6):966-974.
PubMedArticle
29.
American Thyroid Association. Professional guidelines. http://www.thyroid.org/thyroid-guidelines/. Accessed December 23, 2014.
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