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Larotrectinib in NTRK Fusion–Positive Thyroid Cancer: Real-World Case Series

By: Kayci Reyer
Posted: Monday, March 28, 2022

According to a case series presented in JCO Precision Oncology, the selective tropomyosin receptor kinase inhibitor larotrectinib may benefit patients with advanced thyroid cancer who have NTRK gene fusions. Hyunseok Kang, MD, of the University of California, San Francisco, and colleagues sought to determine whether the efficacy of larotrectinib in previous small basket trials could also be found in real-world treatment settings.

The study reviewed the cases of four patients who had all received treatment at a single facility. Anaplastic thyroid cancer (n = 1), poorly differentiated thyroid cancer (n = 1), and papillary thyroid cancer (n = 2) were represented in the study. All patients were continuing to receive larotrectinib at the time the study was written. Patients with poorly differentiated or papillary thyroid cancer (n = 3) achieved durable radiographic response following larotrectinib therapy.

The patient with poorly differentiated disease harbored a TPM3-NTRK1 fusion and achieved a complete response in 2 months of larotrectinib treatment following surgery. She experienced a lasting thyroglobulin increase over baseline.

Both patients with papillary thyroid cancer harbored ETV6-NTRK3 fusions. One patient achieved an ongoing partial response after receiving larotrectinib following the development of postsurgical metastases. One patient achieved an ongoing partial response after receiving larotrectinib following resection and radiation for metastases.

The patient with anaplastic disease harbored an SQSTM1-NTRK3 mutation. Following postthyroidectomy larotrectinib, the patient experienced a 16% reduction in tumor burden over 2 months and disease progression after 6 months.

Disclosure: For full disclosures of the study authors, visit ascopubs.org.


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