Real-Life Experience with Entrectinib in Neurotrophic Tyrosine Receptor Kinase Fusion-Positive Solid Tumors: A Multicenter Retrospective Trial.

Background: Neurotrophic tyrosine receptor kinase (NTRK) gene fusions represent rare somatic mutations in many types of cancer and have enabled the use of promising targeted therapies. In clinical studies, increased response rates to tropomyosin receptor kinase inhibitors have been demonstrated in NTRK fusion-positive cancer types; however, real-world experiences on these targeted agents are scarce.

Objective: We evaluated the clinical characteristics and treatment responses of NTRK fusion-positive patients who received entrectinib treatment within the scope of an early access program in Turkey.

Patients and methods: This multicenter, retrospective analysis involved 17 patients with solid tumors harboring NTRK fusions or rearrangements from 14 oncology centers between June 2019 and 31 March 2024. Demographic and clinical data were obtained via retrospective review of medical records with a cutoff date of 31 March 2024.

Results: The median age at diagnosis of the patients in our study was 42 [interquartile range (IQR) 33-60] years. Nine different types of solid tumors were diagnosed in these patients. The most common NTRK gene rearrangements involved NTRK1 (n = 8), followed by NTRK3 (n = 7). The median duration of entrectinib usage was 6.9 (IQR 3.1-16.1) months. Dose reductions due to side effects were performed in four patients: two due to leukopenia, one due to visual disturbance, and one due to troponin elevation. Leukopenia was the most commonly observed side effect. The objective response rate (ORR) was 35.3% (95% confidence interval (CI) 14.2-62.7), with complete response (CR) achieved in four patients. The duration of response (DOR) in patients who responded after initiating entrectinib was 9.8 (95% CI 0-30.7) months, the median overall survival (mOS) in all patients was 20.8 (95% CI 0-48.5) months, and the time-to-treatment failure (TTF) was 6.4 (95% CI 0-13.5) months.

Conclusions: In this retrospective study, we aimed to obtain real-world data concerning the use of entrectinib in patients with solid tumors harboring NTRK fusion genes. Although our findings are partially similar to the results of clinical studies, prospective studies in larger patient groups with more diverse tumor types and different demographic characteristics are needed to confirm the findings.