NTRK fusion events and targeted treatment of advanced radioiodine refractory thyroid cancer

Purpose Pathogenic fusion events involving neurotrophic receptor tyrosine kinase (NTRK) have been described in similar to 2% of differentiated thyroid cancer (DTC). The selective tropomyosin receptor kinase (TRK) inhibitors entrectinib and larotrectinib have been approved in a tumor agnostic manner based on phase 1/2 clinical trials. In a real-world setting at five referral centers, we aimed to describe the prevalence of NTRK gene fusions and the efficacy and safety of TRK inhibitor treatment for non-medullary, advanced thyroid cancer (TC). Methods A total of 184 TC patients with testing for NTRK gene fusions were included. Progression-free survival (PFS) and overall survival (OS) probabilities were estimated using the Kaplan-Meier method in six patients with NTRK fusion-positive TC who underwent TRK inhibitor therapy. Results 8/184 (4%) patients harbored NTRK gene fusions. Six patients with radioiodine (RAI)-refractory TC harboring NTRK1 (n = 4) and NTRK3 (n = 2) gene fusions were treated with larotrectinib. Five patients (83%) had received >= 1 prior systemic therapy and one patient did not receive prior systemic therapy. All patients had morphologically progressive disease before treatment initiation. Objective response rate was 83%, including two complete remissions. Median PFS from start of TRK inhibitor treatment was 23 months (95% confidence interval [CI], 0-57.4) and median OS was not reached (NR) (95% CI, NR). Adverse events were of grade 1-3. Conclusion The prevalence of NTRK gene fusions in our cohort of RAI-refractory TC is slightly higher than reported for all TC patients. Larotrectinib is an effective treatment option in the majority of NTRK gene fusion-positive advanced TC patients after prior systemic treatment and has a favorable safety profile.

Automated summary

This study aims to describe the prevalence of NTRK gene fusions and the efficacy and safety of TRK inhibitor treatment in non-medullary, advanced thyroid cancer (TC) patients. The results showed that 8 out of 184 patients (4%) had NTRK gene fusions. Among the 6 patients treated with TRK inhibitors, 83% achieved objective response and the median PFS was 23 months. The conclusion of the study is that larotrectinib is an effective treatment option with a favorable safety profile for NTRK gene fusion-positive advanced TC patients after prior systemic treatment.