A population-based study of incidence, diagnostic approaches and therapy of thymic epithelial tumors

Abstract

18086 Background: Diagnostic and therapeutic approaches to thymic epithelial tumors are not standardized. Also, opinions differ on the biological behavior of thymomas. The purpose of this population-based study was to assess the incidence of the whole spectrum of thymomas and thymic carcinomas and to assess the diagnostic approaches, therapy, and survival of these tumors. Methods: The Dutch National Pathological Archives (PALGA) were used to evaluate the incidence of thymomas and other thymus neoplasms between 1994- 2003. Clinical and pathological characteristics were obtained from PALGA and the Netherlands Cancer Registry. Results: We identified 537 thymic epithelial tumors, male/female 262/275, median age 59 years (range 1–94). WHO classification was type A 12%, AB 21%, B1 16%, B2 18%, B3 12%, C 11%, unknown 10%. Clinical disease stage according to Masaoka was I in 26%, II 23%, III 13%, IV 12%, unknown 26%. Incidence of all thymic epithelial tumors in the Netherlands is 3.2/1,000,000 and of thymomas (WHO classes A-B2) is 2.2/1,000,000. Primary resection as first procedure for obtaining a diagnosis was performed in 56% of patients, and was associated with smaller tumors (p<0.001), younger age (p=0.006), and the presence of myasthenia gravis (p<0.001). Survival data were available for 232 patients. Five- year overall observed survival was 69%. Not only thymic carcinomas but also thymomas showed tumor-related mortality. The majority of patients (78%) was treated with resection, and had a better survival than non-operated patients (median survival more than 10 years versus 1.1 years, p<0.001). Among the surgically treated patients (n=180), the completeness of resection was not prognostic (p=0.17). Conclusions: Thymic epithelial tumors are rare and the majority shows tumor-related mortality. Primary resection is the most frequently used procedure to obtain a definite diagnosis and is also advisable in cases with questionable resectability. No significant financial relationships to disclose.