Immune Checkpoint Inhibitors in Unresectable or Metastatic Thymic Epithelial Tumors--A Real-World Assessment of Efficacy and Toxicity.

Thymic epithelial tumors (TET) are rare, with limited prospective data on their management. While studied in the second-line setting and beyond, real-world data on immune checkpoint inhibitors (ICIs) outcomes are lacking. We assessed the real-world efficacy and safety of ICIs in TET, and investigated the correlation between immune-related adverse events (irAEs) and clinical outcomes. We retrospectively reviewed patients with unresectable or metastatic TET treated with ICIs at 5 Mayo Clinic sites. Baseline characteristics, outcomes, and toxicity data were collected. We calculated the overall response rate (ORR), median progression-free survival (mPFS), median overall survival (mOS), and assessed their correlation with irAEs. Thirty patients were included (28 with thymic carcinoma, 2 with thymoma). Pembrolizumab was used in 29 patients, and durvalumab in one. The ORR was 23.3%. The mPFS was 10.12 months and did not differ by irAEs incidence (hazard ratio (HR) 0.99, 95% confidence interval (CI), 0.39-2.54). 40.0% of patients had irAEs, which were predominantly grade 2 (61.5%), and most commonly thyroiditis (26.7%). The mOS was 81.3 months, numerically longer in those with irAEs versus those without (81.3 vs. 58.6 months; HR 0.51, 95% CI, 0.13-1.97). The ORR was similar to data published in the literature, although mPFS and mOS were numerically longer. The incidence of irAEs was higher but less severe than in prior data. irAEs did not significantly correlate with outcomes, despite a trend toward prolonged mOS. Further studies are needed to identify biomarkers, optimize both patient selection and toxicity management, and improve TET outcomes.