545P Real world data of capecitabine plus gemcitabine in thymic epithelial tumors: A retrospective analysis

Background: Thymic epithelial tumors (TETs), including thymoma (T) and thymic carcinoma (TC), are rare malignancies with no standard therapy beyond platinumbased chemotherapy in advanced disease.Capecitabine plus gemcitabine (C+G) have reported 40% of objective response rate (ORR) in a phase II trial (n=30), but realworld evidence remains scarce. Methods:We retrospectively identified patients (pts) with TETs treated with C+G as 2nd-line therapy within the French RYTHMIC network (2016)(2017)(2018)(2019)(2020)(2021)(2022)(2023)(2024)(2025).PFS and overall survival (OS) were calculated from treatment start, estimated through Kaplan-Meier curves and compared via log-rank test.Multivariable Cox models were conducted including histology, ECOG PS, and liver metastases.Toxicity was graded according to CTCAE v5.Results: Overall, 38 pts (22 TC, 16 T) received C+G.Median age was 50 years, 39% were female, 81% had a PS 0-1 and 76% received C+G as 3rd-line.Autoimmune diseases occurred in 5% of TC and 31% of T. Among 36 pts evaluable for response, ORR was 39% (35% in TC; 44% in T).In the overall cohort (n = 38), with a median follow-up of 46.5 months, the median PFS was 5.8 months (95% CI: 4.5-9.7),while the median OS was 25.6 months (95% CI: 17.8-62.3).When stratified by histology, pts with TC had a median PFS of 5.0 months and a median OS of 16.9 months, whereas those with T achieved a median PFS of 5.9 months and a median OS of 34.0 months (Table ).At multivariate analysis, ECOG PS 2 was independently associated with worse PFS and OS.Among 28 pts with available safety data, grade 3 toxicities included thrombocytopenia (14%), neutropenia (7%), and anemia (7%); fatigue (36%), hand-foot syndrome (28%), and mucositis (11%) were the most common grade 1-2 events.No treatment-related deaths occurred; one patient discontinued due to toxicity. Conclusions:In this real-world cohort, C+G showed clinically meaningful activity and manageable toxicity in advanced TETs, supporting its use in later-line settings.