The changing incidence of thyroid cancer

Abstract

During the past few decades, the incidence of thyroid cancer has increased substantially in many countries, including the USA. The rise in incidence seems to be attributable both to the growing use of diagnostic imaging and fine-needle aspiration biopsy, which has led to enhanced detection and diagnosis of subclinical thyroid cancers, and environmental factors. The latest American Thyroid Association (ATA) practice guidelines for the management of adult patients with thyroid nodules and differentiated thyroid cancer differ substantially from the previous ATA guidelines published in 2009. Specifically, the problems of overdiagnosis and overtreatment of a disease that is typically indolent, where treatment-related morbidity might not be justified by a survival benefit, now seem to be acknowledged. As few modifiable risk factors for thyroid cancer have been established, the specific environmental factors that have contributed to the rising incidence of thyroid cancer remain speculative. However, the findings of several large, well-designed epidemiological studies have provided new information about exposures (such as obesity) that might influence the development of thyroid cancer. In this Review, we describe the changing incidence of thyroid cancer, suggest potential explanations for these trends, emphasize the implications for patients and highlight ongoing and potential strategies to combat this growing clinical and public health issue.

FIG. 1 |

Trends in total and histology-specific thyroid cancer incidence (SEER 13) and total thyroid cancer mortality (USA) from 1993–2012. Rates are age-adjusted (2000 US standard population) and each point represents 4 years. Incidence data are from the SEER 13 areas (San Francisco, Connecticut, Detroit, Hawaii, Iowa, New Mexico, Seattle, Utah, Atlanta, Rural Georgia, Los Angeles, San Jose-Monterey and the Alaska Native Registry); thyroid cancer cases are restricted to those microscopically confirmed and exclude cases identified only by autopsy or death certificates. Mortality data are from the US Mortality Files, National Center for Health Statistics, Center for Disease Control and Prevention. Annual percent change (APC) based on rates age-adjusted to the 2000 US standard population (19 age groups – Census P25–1130). *APC is significantly different from zero (P <0.05).