Work

UH cancer center hotline: thyroid cancer: rising incidence and ethnic disparities.

Year: 2012

Type: article

Abstract: The incidence of thyroid cancer has been steadily increasing in the United States over the past several decades. This trend is counter to that of most major cancers, which have experienced decreasing rates in the United States.1 From 1975 to 2007, thyroid cancer rates more than doubled in the United States.2 Although rates have been rising in both males and females, the increase has been most pronounced in women,2 who traditionally have had 2 to 3-fold the risk of men. In 2003–2007, the age-adjusted incidence of thyroid cancer was 15.2 per 100,000 in females compared to 5.2 per 100,000 in males.2 Today thyroid carcinoma is the fifth most common cancer among US women.1 The increase in thyroid cancer has been primarily observed for papillary carcinomas, the most common histologic form.3,4 It has been suggested that rising rates can be attributed to increased medical surveillance resulting in more frequent detection of small papillary tumors.4 Nonetheless, national data have demonstrated increases in both large and small tumors indicating that the rising incidence can only partially be artifactual due to surveillance.3,5 The etiology of thyroid cancer is largely unknown and few risk factors are recognized. Exposure to ionizing radiation, family history, and a history of goiter or benign thyroid disease are among the only established risk factors.6–8 Other possible risk factors include excess weight,9–11 oral contraceptive use,12 history of miscarriage,11 use of fertility drugs,11 advanced age at pregnancy,13 and excessive intake of seafood and dietary iodine.11 There is also some evidence of a protective effect of cigarette smoking and consumption of cruciferous vegetables11,13–15 and, in areas of iodine deficiency, intake of fish.16 The pronounced gender disparity suggests that hormones play an important role in the etiology of thyroid cancer. Estrogen receptors are widely expressed in neoplastic thyroid tissue and there is evidence that estrogen may contribute to thyroid carcinogenesis.17,18 Certain environmental chemicals can disrupt the action of thyroid stimulating hormone, which regulates the growth and function of the thyroid gland.19 Genetic alterations have been suggested including the association of mutations in RET and BRAF with increased thyroid cancer risk.20 Hawai‘i has among the highest incidence rates of thyroid cancer in the country.21 Annually, approximately 160–200 Hawai‘i residents are diagnosed with this malignancy. Substantial racial and ethnic disparities have been observed. From 2000–2005, among the major ethnic groups in Hawai‘i, the age-adjusted incidence among women was highest in Filipinas (27.7 per 100,000) and lowest in Japanese (9.1 per 100,000) (Figure 1). Filipino men were also disparately affected (9.5 per 100,000) compared to males of other ethnic groups. Data from the Hawai‘i Tumor Registry of the National Cancer Institute's Surveillance, Epidemiology, and End Results program reveal some differences in Filipino and non-Filipino patients in Hawai‘i. Papillary tumors comprised a greater proportion of thyroid cancers in Filipino patients compared to other groups (P = 0.004). Historically, thyroid cancer rates have been higher for Filipinas born in the Philippines than for those born in Hawai‘i. However, this gap has been attenuated in recent years with rates in Hawai‘i-born nearly equal to that of Philippine-born Filipinas. The excess risk observed amongst Hawai‘i's Filipinos has also been observed in Filipinos living in other parts of the United States.22–24 Figure 1 Invasive thyroid cancer incidence, Hawai‘i 2000–2005 (Age-adjusted to United States 2000 Standard) Future research is necessary to address the causes of thyroid cancer in order to develop strategies to curb this growing epidemic. The underlying reasons for the disparate risk among Filipinos remain unexplained and may provide clues to the pathogenesis of this malignancy.

Source: PubMed

Authors: Brenda Y Hernandez, Shane Y Morita, Lynne R Wilkens

Institution: University of Hawaii Cancer Center

Language: English

Topic: Thyroid Cancer Diagnosis and Treatment

Subfield: Endocrinology, Diabetes and Metabolism

Field: Medicine

Domain: Health Sciences

SDG: Good health and well-being

Open Access status: green

Funders: National Cancer Institute, National Institute on Minority Health and Health Disparities

Awards: RCMI Multidisciplinary And Translational Research Infrastructure EXpansion (RAMAT, University of Hawaii Cancer Center CCSG