Tremelimumab In Combination With Microwave Ablation In Patients With Refractory Biliary Tract Cancer (Btc).

365 Background: Treatment option for patients with advanced BTC is limited and prognosis is poor with a median survival of less than 1 year in the locally advanced or metastatic setting. It has been shown deregulation of the immune system plays an important role in the pathogenesis of BTC. This study aimed to investigate whether tremelimumab (Treme), anti-CTLA4, could be combined safely and feasibly with microwave ablation therapy to enhance the effect of anti-CTLA4 treatment in patients with advanced BTC. Methods: Patients with refractory BTC were enrolled in a study of monthly Treme (10mg/kg, IV, 6 doses), followed by 3-monthly infusions until off-treatment criteria were met. On day 36, patients underwent subtotal microwave ablation. Staging image was performed every 8 weeks. Adverse events (AEs) were collected and managed. Tumor samples and peripheral blood samples were collected to perform immune monitoring. Results: Twenty patients with refractory BTC were enrolled. Male: female ratio was 10:10 with median age 56.5 years (range 37-67). Six patients had extrahepatic cholangiocarcinoma (ECC), two patients had gallbladder cancer, whereas the remaining 12 patients had intrahepatic cholangiocarcinoma (ICC). No dose-limiting toxicities were encountered. The common AEs included lymphocytopenia, colitis, adrenal insufficiency, anemia, and elevated transaminases. The most common clinical toxicity was diarrhea. Sixteen patients were evaluable for response analysis, one (6%) patient achieved a confirmed partial response (lasting for 8 months), 6 (37.5%) achieved stable disease with the longest lasting for 9.2 months. Among all 20 patients, median progression free survival, time to progression, and overall survival were 3.4 months (95% CI 2.5-5.2 months), 3.3 months (95% CI: 2.5-4.6 months) and 6.0 months (95% CI 3.8-8.8 months) respectively in this small pilot cohort. T cell receptor (TCR) b screening showed Treme expanded TCR repertoire though non-significantly. RNA seq is ongoing and will be presented. Conclusions: Treme in combination with tumor ablation is a potential new treatment for patients with advanced BTC. TCR repertoire expansion induced by Treme may contribute to treatment benefit. Clinical trial information: NCT01853618.