Abstract 3418: A phase II basket trial of dual anti-CTLA-4 and anti-PD-1 blockade in rare tumors (DART) SWOG S1609: The salivary gland tumor cohort

Background: The potential therapeutic benefits of checkpoint inhibitors and their application to many different tumor types has been a key factor in the advancement of medical oncology since their first approval for metastatic melanoma in 2011. However, their efficacy in rare tumor types remains to be seen. This paper presents the results of combination therapy with both anti-CTLA and anti-PD-1 in the small bowel cohort of SWOG S1609 Dual Anti-CTLA-4 & Anti-PD-1 blockade in Rare Tumors (DART). Methods: This study is designed as a prospective, open-label, multicenter phase 2 clinical trial of ipilimumab (1mg/kg intravenously every 6 weeks) plus nivolumab (240mg intravenously every 2 weeks) in rare tumors. Here we report the outcomes from patients diagnosed with small bowel cancer (SBC). The primary endpoints included overall response rate (ORR) (RECIST v1.1) (complete response (CR) and partial responses (PR)); progression-free survival (PFS), overall survival (OS), stable disease >6 months, and toxicity were the secondary endpoints. Results: Twenty five patients were registered to the cohort and twenty three received therapy. The duodenum was the primary site of origin in 52% (N=11), 14% (N=3) arose in the ileum and 14% (N=3) arose in the jejunum. The primary site of origin was unknown in 19% (N=4). The overall response rate was 8% (CR, 4%, N= 1; PR, 4%, N= 1). The median PFS was 2 months; 6-month OS was 48% and median OS 6 months. The most common toxicities were diarrhea and fatigue (both 17%) followed by dyspnea (13%) with diarrhea, increased bilirubin, colitis and elevated lipase (all 4.3%) as the most common grade 3-5 immune-related adverse events. Conclusions: Combination therapy with ipilimumab plus nivolumab in small bowel tumors resulted in an overall response rate of 8% with one partial and one complete response in twenty three treated patients. Citation Format: Young Kwang Chae, Megan Othus, Sandip Pravin Patel, Mark Zalupski, Anup Kasi, Maged Khalil, Aparna Kalyan, Blase Polite, Sarah Fenton, Sewan Gurung, Christine M. McLeod, Francis Giles, Helen X. Chen, Elad Sharon, Edward Mayerson, Melissa Plets, Christopher W. Ryan, Charles D. Blanke, Razelle Kurzrock. A phase II basket trial of dual anti-CTLA-4 and anti-PD-1 blockade in rare tumors (DART) SWOG S1609: The small bowel tumor cohort [abstract]. In: Proceedings of the Annual Meeting of the American Association for Cancer Research 2020; 2020 Apr 27-28 and Jun 22-24. Philadelphia (PA): AACR; Cancer Res 2020;80(16 Suppl):Abstract nr 3417.