Outcomes of thymic epithelial tumors (TETs) with pleural metastases: Real-world insight from RYTHMIC.

Abstract

8578 Background: TETs are rare and potentially aggressive malignancies with high associated prevalence of autoimmune disorders (AIDs). The pleura is the main metastatic site at relapse, referred as Masaoka-Koga stage (MK) IVa. The benefit of surgical management is unknown, so we have collected outcomes of patients with MK IVa TETs in a large prospective database. Methods: RYTHMIC (Réseau tumeurs THYMiques et Cancer) is a French nationwide network mandated to systematically discuss every case of TETs. The database, hosted by IFCT (Intergroupe Francophone de Cancérologie Thoracique), prospectively includes all consecutive pts with a diagnosis of TET discussed in RYTHMIC national or regional tumor boards. We analyzed epidemiologic, clinical and pathological characteristics of patients (pts) with MK IVa TETs. Results: From January 2012 to December 2019, 2909 pts were included in the database, including 182 MK IVa (6.2%). The median age at diagnosis was 63.5 (range 9 to 91). 58/182 (32%) pts reported AIDs, 76% myasthenia gravis. 129/182 pts had synchronous pleural metastasis. 118/182 (65%) tumors were resected, of them 10 (8.4%) had only pericardial metastases. Thymoma (T) B2 rate was 35.6%, B3 17.8% and thymic carcinoma (TC) 13.5%. Induction chemotherapy (CT) was given in 46 (39%) T and 10 (8%) TC with response rate of 50% and 70% respectively. Thymectomy was performed in addition to pleurectomy in 44 pts (37.2%), pericardiectomy in 68 (57.6%), lung resection in 80 (67.8%) or pneumonectomy in 15 (12.7%). Node resection was performed in 57.6% (n = 67), 12 (18%) were positive. The complete resection rate assessed by surgeons was 57% with a median of 15 (0 to 28) resected pleural metastasis. Intrapleural chemotherapy was added for 19 (16%) pts. No mortality was reported 90 days after surgery procedure. Median follow-up was 36 months. Pleural recurrence was seen in 47 (72%) pts. Median disease-free survival (DFS) was 39 vs 16 months in resected vs not resected tumors (p < 0.0001), 5-years overall survival (OS) was 88 vs 66% (p = 0.28), respectively. Risk of relapse decreased by 60% with surgery (HR = 0.4, 95CI (0.25-0.62); p < 0.0001). Conclusions: The prevalence of MK IVa in our cohort was 6.2%. Surgery appears to be a safe and valid option for pts with MK IVa TET at diagnosis.