Thymic neuroendocrine tumors: an analysis of 18 cases and a literature review

Background: Thymic neuroendocrine tumors (TNETs) are exceedingly rare, and there are no uniform treatment strategies. Methods: Between September 1993 and March 2015, 18 patients diagnosed with histologically confirmed TNETs and treated at the Fudan University Shanghai Cancer Center were reviewed. Overall survival (OS), progression-free survival (PFS) and disease-free survival (DFS) were analyzed using the Kaplan-Meier method. The prognostic factors [sex, age, stage, tumor size (TS), grade, adjuvant therapy, and surgery status] for PFS and OS were analyzed. Results: Thirteen patients underwent surgical resection: 53.5% underwent complete tumor resection (R0), and 46.2% had a macroscopically residual disease (R2). Eleven patients received adjuvant treatment postoperatively [chemotherapy (CT) combined radiotherapy (RT), 7; RT, 3; and CT, 1]. Well-differentiated neuroendocrine carcinomas (n= 12/18 patients; 66.7%); poorly differentiated neuroendocrine carcinomas (n= 6/18 patients; 33.3%). Masaoka-Koga stages (MK) I, III, and IVb were observed in 1, 8, and 9 patients, respectively. The 5-year OS and 5-year PFS rates were 67.7% and 37.9%, respectively. The 5-year DFS rate in the patients with R0 resection was 66.7%. In univariate analysis, OS was significantly influenced by the grade (P < 0.05), surgery status (P < 0.05). PFS was significantly influenced by the surgery status (P < 0.05). Conclusions: Adequate surgical resection is a strong prognostic factor. Adjuvant RT contributes to controlling local recurrence (LR) to improve OS and PFS. Patients with well-differentiated TNET have a better OS. Additionally, an active treatment after recurrence will greatly benefit patients' OS.