National incidence and initial therapy for thymic carcinoma in Japan: based on analysis of hospital-based cancer registry data, 2009–2015

Abstract

Background Although thymic carcinoma is a rare epithelial neoplasm that tends to be aggressive and metastasize widely, its incidence in Japan remains unclear. This study was to examine the incidence and initial treatment of thymic carcinoma in the Japanese population using data from a hospital-based cancer registry. Methods Using data from the national database of hospital-based cancer registries, we examined the incidence and initial treatment of thymic carcinoma diagnosed and treated in designated and non-designated cancer care hospitals between 2009 and 2015. Based on Japanese population estimates, we calculated the incidence rate of thymic cancer in Japan. Results A total of 2587 thymic carcinoma cases were diagnosed between 1 January 2009 and 31 December 2015. These patients consisted of 1705 (66%) men and 882 (34%) women, with a median age of 65.5 years (range, 16–96 years). The number and proportion of thymic carcinoma to all registered cancer cases per year increased each year. The incidence rate was estimated to be 0.29/100000 during the observation period, with an annual onset incidence of 0.38/100000 in 2015. Almost half of all cases of thymic carcinoma were treated surgically, while the others were treated with non-surgical therapy consisting of chemotherapy with or without radiotherapy. Conclusions We estimated the incidence rate of thymic carcinoma in Japan based on the designated cancer care hospital-based cancer registry. The half of all patients with thymic carcinoma was unfit for multimodality therapy, including thoracic surgery.