Secular Trend in the Incidence of Japanese Employees With Thyroid Cancer Undergoing Thyroidectomy From 2005 To 2014: A Retrospective Descriptive Study Using An Employment-based Insurance Claims Database - Secular Trend in the Incidence of Japanese Employees With Thyroid Cancer Undergoing Thyroidectomy From 2005 To 2014: A Retrospective Descriptive Study Using An Employment-based Insurance Claims Database - Open Access Pub

This study aimed to investigate the trend of patients with thyroid cancer undergoing thyroidectomy and those undergoing fine needle aspiration (FNA) and its relationship with thyroid cancer, using a large-scale, real-world database established based on the employment-based health insurance claims data in Japan. In this retrospective descriptive study, annual incidence rates of patients with thyroid cancer undergoing thyroidectomy and FNA from 2005 to 2014 were calculated. Among the 3,130,757 enrollees, 926 patients were diagnosed with thyroid cancer and underwent thyroidectomies. The annual incidence of patients with thyroid cancer undergoing thyroidectomy increased from 5.4 (95% confidence interval 95% CI, 3.4–8.5) in 2005 to 11.7 (10.1–13.5) per 100,000 patient-years in 2013, with a gradual increase among patients in their 20s and 30s and with the most notable increase among those in their 40s and 50s. The annual FNA rate also increased during those years, whereas no noticeable change was observed in the thyroid cancer detection rate. The incidence rates of patients with thyroid cancer undergoing thyroidectomy and those undergoing FNA were strongly correlated, with Pearson’s correlation coefficients of 0.935 for men and 0.886 for women. In conclusion, an increasing trend in the incidence of patients with thyroid cancer undergoing thyroidectomy was observed from 2005 to 2013 among a large group of Japanese employees of working age and their dependents. These results provide useful information on the impact of patients with thyroid cancer undergoing thyroidectomy on the working population. DOI10.14302/issn.2574-4496.jtc-18-2473 Thyroid cancer is the most common form of endocrine cancer. Its incidence in the last few decades has increased worldwide 1, 2, with an average increase of 48.0% and 66.7% among men and women, respectively, over two periods, 1973–1977 and 1998–2002 in the Americas, Asia, Europe, and Oceania 1. The estimated incidence rate in Japan also continuously increased from 5.7 to 10.9 per 100,000 individuals from 2002 to 2012. However, the estimate was based on patient statistics derived from prefectural registries and did not include all prefectures 3. One of the possible explanations behind the increasing incidence is the detection of a greater number of thyroid cancer cases due to an increased number of individuals who underwent screening and diagnostic tests 4. A growing number of screening tests for thyroid cancer, including ultrasound, are performed globally 4, 5, 6. In Japan, thyroid cancer screening has been increasingly conducted