Larotrectinib Treatment for Patients With TRK Fusion-Positive Salivary Gland Cancers

Abstract

Background: Larotrectinib is a first-in-class, highly selective, and central nervous system-active tropomyosin receptor kinase (TRK) inhibitor approved for the treatment of adult and pediatric patients with TRK fusion cancer. We report the efficacy and safety of larotrectinib in patients with TRK fusion-positive salivary gland cancers. Patients and Methods: Patients with TRK fusion-positive salivary gland cancer treated with larotrectinib were identified from two clinical trials (NCT02122913 and NCT02576431). Patients received larotrectinib 100 mg twice daily (BID) except for one patient who received 150 mg BID in the phase I trial. The primary endpoint was objective response rate (ORR) as assessed by the investigator using Response Evaluation Criteria in Solid Tumors version 1.1. Results: At the data cut-off (July 20, 2020), 24 patients with TRK fusion-positive salivary gland cancer had been treated. The most common histologies were secretory carcinoma (54%), adenocarcinoma (25%), and mucoepidermoid carcinoma (13%). All 24 patients had an ETV6-NTRK3 gene fusion. The ORR was 92% (95% confidence interval, 73-99). Best overall response was complete response in three (13%) patients, partial response in 19 (79%), and progressive disease in two (8%). The rate of progression-free survival at 24 months was 78% (median follow-up 30.9 months). Most treatment-related adverse events (AEs) were grade 1-2, and no patients discontinued treatment due to AEs. Conclusion: Larotrectinib demonstrated robust and durable efficacy in patients with TRK fusion-positive salivary gland tumors of various histologies, and a favorable safety profile. These findings support NTRK gene fusion testing in patients with advanced salivary gland cancers.