Original Article in J Thoracic Oncology Characterization, prognosis, and treatment of patients with locally advanced or metastatic thymic neuroendocrine tumor (Thy-NET): a retrospective study of the French GTE, ENDOCAN RENATEN and RYTHMIC networks.

Introduction: Thymic neuroendocrine tumors (Thy-NET) constitute a poorly characterized ultra-rare subgroup of NET.

Objective: 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: Seventy-four patients (median age, 46-years) followed in 20 French centers between 1988 and 2020 were included. Main characteristics were: male over female ratio: 2.7, MEN-1 inherited syndrome in 25 patients (34%), NET G2 atypical carcinoids in 31 (48%) patients, and 20 patients (31%) with NET G3 highly proliferative atypical carcinoids, 11 (15%) patients with ectopic Cushing syndrome. Metastatic sites were: lymph nodes (54 patients, 73%), bone (42 patients, 65%), lung (31 patients, 42%) and pleura (31 patients, 42%). Sixty-four (87%) patients had locally advanced Thy-NET and 8 (11%) had synchronous metastases, at diagnosis. Pleural metastases were almost exclusively metachronous. Positive 18F-FDG or 68Ga-DOTATOC-PET was found in 88% or 100% of cases, respectively. The 5-years 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 MEN1 patients. Partial responses were more frequently observed in patients treated with cytotoxic chemotherapy.

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