Characterization, Prognosis, and Treatment of Patients With Locally Advanced or Metastatic Thymic Neuroendocrine Tumor: A Retrospective Study of the French GTE, ENDOCAN RENATEN, and RYTHMIC Networks.

INTRODUCTION

Thymic neuroendocrine tumors (Thy-NETs) constitute a poorly characterized ultrarare subgroup of NET. To characterize locally advanced or metastatic Thy-NET, to evaluate prognostic factors for survival, and to provide an overview of their current therapeutic management in two dedicated French national networks.

METHODS

Retrospective multicenter study of two French ENDOCAN-RENATEN and RYTHMIC networks.

RESULTS

A total of 74 patients (median age, 46 y) followed in 20 French centers between 1988 and 2020 were included. Main characteristics were as follows: male over female ratio of 2.7, multiple endocrine neoplasia type 1 inherited syndrome in 25 patients (34%), NET G2 atypical carcinoids in 31 patients (48%), 20 patients (31%) with NET G3 highly proliferative atypical carcinoids, and 11 patients (15%) with ectopic Cushing syndrome. Metastatic sites were as follows: lymph nodes (54 patients, 73%), bone (42 patients, 65%), lung (31 patients, 42%), and pleura (31 patients, 42%). A total of 64 patients (87%) had locally advanced Thy-NET and eight (11%) had synchronous metastases, at diagnosis. Pleural metastases were almost exclusively metachronous. Positive results for 18F-FDG or somatostain receptor imaging was found in 88% or 74% of cases, respectively. The 5-year overall survival was 85%. Univariate analysis on overall survival reveals a trend toward worse prognosis in case of female gender and bone metastases and better prognosis for patients with multiple endocrine neoplasia type 1. Partial responses were more frequently observed in patients treated with cytotoxic chemotherapy.

CONCLUSION

This large series identifies specific characteristics of patients with advanced Thy-NET. Prognosis was better than previously reported. Perioperative pleural dissemination is suspected. Partial responses were mainly observed with chemotherapy.