ECE2021 Oral Communications Oral Communications 10: Thyroid (6 abstracts)
Rearrangement involving one of the neurotrophic-tropomyosin receptor kinase (NTRK) genes belonging to the NTRK family represents a significant oncogenic event in thyroid cancer (TC). Recently, there has been a growing interest in testing and characterizing NTRK fusion genes because they are therapeutically targetable. This study aimed to determine a frequency, clinical and histopathological features of a large cohort of NTRK fusion-positive TC and mainly to determine the prognostic significance of NTRK fusion genes based on long-term follow-up of patients with TC harboring this mutation.
The cohort consisted of 989 different TC tissue samples. Based on the detected mutation, samples were triaged. Samples positive for the BRAF, HRAS, KRAS, NRAS, RET, RET/PTC or PAX8/PPARGγ mutation were excluded from the further NTRK fusion gene analyses. RNA from 259 samples was analysed using the NTRK Gene Fusions Detection Kit (AmoyDx) by Real-Time PCR (LC480, Roche) or using the FusionPlex Comprehensive Thyroid and Lung panel (ArcherDx) by next generation sequencing using MiSeq (Illumina).
NTRK fusion genes were detected in 57 of 846 (6.7%) papillary thyroid cancer (PTC) and in 2 of 10 (20.0%) poorly differentiated thyroid cancer (PDTC). A total of eight types of NTRK fusions were found, including ETV6/NTRK3, EML4/NTRK3, RBPMS/NTRK3, SQSTM1/NTRK3, TPM3/NTRK1, IRF2BP2/NTRK1, SQSTM1/NTRK1, TPR/NTRK1. In PTC, a follicular growth pattern was identified in 78.0% of NTRK fusion-positive cases, and both cases of PDTC dedifferentiated from PTC with a mixed papillary and follicular growth pattern. Lymph node and distant metastases were found in 54.2% and 6.8% of cases, respectively. Initially within 2 years of postoperative treatment, 58.9% of NTRK fusion-positive patients had an excellent response (ER), 16.1% had an indeterminate response (IR) and 25.0% of patients had a structural incomplete response (SIR) to treatment. During the follow-up, response to treatment had an improving tendency. After 10 years of follow-up, 82.3% of patients had ER, 11.8% had IR, 5.9% had a biochemical incomplete response, no patient had SIR, and three patients died.
In summary, NTRK fusions are rare markers occurring mostly in PTC but also in PDTC. Patients without metastases had a favourable prognosis and patients with metastases often suffered from persistent disease. The genetic molecular testing of NTRK fusions is important not only for patients diagnosis and prognosis, but also for possible targeted therapy with Trk inhibitors.
Supported by the Ministry of Health of the Czech Republic DRO (Institute of Endocrinology EU, 00023761) grant.
22 May 2021 - 26 May 2021