A phase II study of pembrolizumab for patients with previously treated advanced thymic epithelial tumor.

8521Background: No standard treatment exists for patients with thymic epithelial tumor (TET) who progress after platinum-containing chemotherapy. We conducted a phase II study of pembrolizumab in patients with TET to evaluate the efficacy and safety. Methods: Between March 2016 and December 2016, patients with histologically confirmed TET who progressed after platinum-containing chemotherapy were eligible. Patients were excluded if they had an active autoimmune disease requiring systemic treatment within the past one year. Patients received 200mg of pembrolizumab intravenously every 3 weeks until tumor progression or unacceptable toxicity. The trial was registered with ClinicalTrials.gov, number NCT02607631. Results: 33 patients were enrolled, 26 with thymic carcinoma (TC) and 7 with thymoma (T). 19 (57.3%) patients received ≥ 2 prior lines of systemic chemotherapy. Median number of cycles was 8 (ranges, 1-13) and median follow up was 6.3 months (ranges, 1.4-9.9). Of 33 patients, 8 (24.2%) achieved partia...