The incidence of thyroid cancer, currently the fifth most common cancer among women in the United States, has been increasing at an alarming rate worldwide. Furthermore, most thyroid cancer is diagnosed among individuals in their 40s, and survivors suffer a high risk of developing a second primary cancer. To elucidate the potential causes of this problem, we have demonstrated that about half of the increase can be explained by “over-diagnosis” due to the density of endocrinologists, the liberal use of cervical ultrasound, and the propensity to biopsy sub-centimeter thyroid nodules; however, changing environmental factors also contribute to the observed trend.
To decipher the environmental causes, we have led a population-based case-control study of thyroid cancer in Connecticut and a nested case-control study of thyroid cancer in the Department of Defense Serum Repository cohort. Recent findings from the population-based case-control study provide the first direct evidence that diagnostic x-rays, particularly nuclear medicine tests and CT scans, might increases the risk of thyroid microcarcinoma, which accounts for approximately half of newly diagnosed thyroid cancers. We are currently testing the novel hypothesis that a widely used flame retardant (polybrominated diphenyl ethers, PBDEs) found in many household products, which bears a structural similarity to thyroid hormones, is associated with an increased risk of thyroid cancer. Our research in this area includes investigation of the combined effect of co-exposure to PBDEs and other structurally similar pollutants on thyroid cancer risk and the examination of new, replacement flame retardants and thyroid cancer risk. We are also exploring genetic susceptibility, gene-environment interaction, and other potential risk factors, including occupational exposures, alcohol consumption, dietary patterns, obesity and physical activity, metals, and other newly emerging chemicals and their mixtures, in relation to thyroid cancer.
Funding for this research provided by the American Cancer Society and the National Institutes of Health.
- Kilfoy B, Zheng T, Han X, Ward MH, Sjodin A, Zhang YQ, Bai Y, Zhu C, Guo GL, Rothman N, Zhang Y. International patterns and trends in thyroid cancer incidence, 1973-2002. Cancer CausesControl 2009; 20(5): 525-31 PMID: 19016336
- Zhu C, Zheng T, Kilfoy B, Han X, Ma S, Ba Y, Bai Y, Wang R, Zhu Y, Zhang Y. A birth cohort analysis of the incidence of papillary thyroid cancer in the United States, 1973-2004. Thyroid 2009; 19(10): 1061-6 PMID: 19732011
- Zhang Y, Guo G, Han X, Zhu C, Kilfoy B, Zhu Y, Boyle P, Zheng T. Do polybrominated diphenyl ethers (PBDEs) increase the risk of thyroid cancer? Biosci Hypotheses 2008; 1:195-9 PMID: 19122824
- Kilfoy B, Devesa S, Ward M, Zhang Y, Rosenberg P, Holford, Anderson W. Gender is an age-specific effect modifier for papillary cancers of the thyroid gland. Cancer Epidemiol Biomarkers Prev 2009; 18(4): 1092-100 PMID: 19293311
- Kilfoy B, Zhang Y, Park Y, Holford T, Schatzkin A, Hollenbeck A, Ward M. Dietary nitrate and nitrite and the risk of thyroid cancer in NIH-AARP diet and health study. In J Cancer 2011; 129(1): 160-72 PMID: 20824705
- Udelsman R, Zhang Y. The epidemic of thyroid cancer in the United States: the role of endocrinologists and ultrasounds. Thyroid 2014; 24(3): 472-9 PMID: 23937391
- Kim C, Bi X, Pan D, Chen Y, Carling T, Ma S, Udelsman R, Zhang Y. Risk of secondary cancer after diagnosis of thyroid cancer primary is elevated in microcarcinomas. Thyroid 2013; 23(5): 575-82 PMID: 23237308
- Aschebrook-Kilfoy B, DellaValle CT, Purdue M. Kim C, Rothman N, Zhang Y, Sjodin A, Ward M. Polybrominated diphenyl ethers and thyroid cancer risk in the Prostate, Colorectal, Lung, and Ovarian Cancer Screening Trial cohort. Am J Epidemiol 2015 181(11): 883-8. PMID: 25939348
- Ba Y, Huang H, Lerro C, Li S, Zhao N, Li A, Ma S, Udelsman R, Zhang Y. Occupation and thyroid cancer: a population-based case-control study in Connecticut. J Occup Environ Med 2016 58(3): 299-305. PMID: 2694881