A phase II basket trial of DART SWOG S1609: the salivary gland tumor cohort

Background: Anti-programmed death-1 (PD-1)/cytotoxic T lymphocyte antigen-4 antibodies are efficacious in various malignancies. The potential role of dual checkpoint inhibitors in many rare solid tumors is not established. Objectives: This study presents the results of ipilimumab–nivolumab in salivary gland neoplasm cohorts of the SWOG S1609 dual anti-CTLA-4 and anti-PD-1 blockade in rare tumors (DART) trial. Design: DART is a prospective, open-label, multicenter (1016 US sites), multi-cohort phase II trial of ipilimumab (1 mg/kg intravenously (IV) every 6 weeks) plus nivolumab (240 mg IV every 2 weeks). Methods: We performed a prospective, multicenter phase II clinical trial of ipilimumab (1 mg/kg IV every 6 weeks) plus nivolumab (240 mg IV every 2 weeks) in three salivary gland neoplasm cohorts: major and minor salivary gland and adenoid cystic cancers. Patients with adenoid cystic salivary gland tumors ( N = 26) and other salivary gland neoplasms ( N = 34) were evaluable. The most common site of origin was the parotid (31%, N = 8 adenoid cystic group; 68%, N = 23 remaining histologies). Results: In the adenoid cystic group, objective response rate (ORR), 4% (complete response (CR) 0%, N = 0; partial response (PR) 4%, N = 1); 6-month progression-free survival (PFS) and overall survival (OS), 32% (95% confidence interval (CI) 18%–57%) and 84% (95% CI 71%–100%), respectively. In the remaining histologic subtypes, the confirmed ORR was 9% (CR, 0%, N = 0; PR, 9%, N = 3); stable disease (SD) >6 months/PR/unconfirmed PR = 35%; 6-month PFS and OS, 34% (95% CI 21%–55%) and 88% (95% CI 78%–100%), respectively. The most common toxicities were fatigue (39%) and diarrhea (26%); diarrhea (8%) was the most common grade 3–4 immune-related adverse event. Conclusion: In salivary gland tumors, combined ipilimumab plus nivolumab resulted in only a 4% ORR in adenoid cystic carcinoma and 9% in all other histologies combined, though the latter showed clinical benefit (included SD >6 months) in 35% of patients. Trial registration: ClinicalTrials.gov registry: NCT02834013.