Highly concordant key genetic alterations in primary tumors and matched distant metastases in differentiated thyroid cancer.

Highly concordant key genetic alterations in primary tumors and matched distant metastases in differentiated thyroid cancer.

Thyroid. 2016 Mar 14;

Authors: Sohn SY, Park WY, Shin HT, Bae JS, Ki CS, Oh YL, Kim SW, Chung JH

Abstract
BACKGROUND: Distant metastases uncommonly occur in differentiated thyroid carcinoma (DTC), but they are a frequent cause of thyroid cancer-related death. Genomic alterations in metastatic tumors, and the relationship with their corresponding primary tumors in DTC, are poorly understood. The objective of this study was to investigate whether genetic alterations in primary tumors are concordant with distant metastases in DTC patients.
METHODS: Surgical samples from primary and matched distant metastatic tumor pairs from 17 DTC patients, and three additional unpaired metastatic tumors from two patients, were analyzed using targeted next generation sequencing (Ion Torrent Ampliseq cancer panel) with a focus on known recurrent somatic mutations in thyroid cancer. Additionally, TERT promoter mutations were assessed by direct sequencing methods.
RESULTS: BRAF mutations were found in 8 of 10 patients with papillary thyroid carcinoma (PTC). NRAS mutation was detected in one patient with follicular variant PTC. TERT promoter mutations were detected in 8 of 10 patients with PTC and most were coexistent with BRAF mutation (7 of 8 BRAF-positive and one BRAF-negative PTC patients). In follicular thyroid carcinoma (FTC), NRAS was the most frequently observed mutation (4 of 9 patients), followed by HRAS (2 patients) and KRAS (one patient). TERT promoter mutations were found in 6 of 7 RAS positive FTC patients. Key somatic alterations such as BRAF and RAS mutations were highly concordant between primary and matched metastatic tumors without discrepancies. The BRAF or RAS mutant allelic frequency was higher in matched metastatic tumors than in the corresponding primary tumors (35% vs. 25% for BRAF mutation, P=0.04 and 40% vs. 34% for RAS mutation, P=0.002). TERT promoter mutations were also mostly concordant in matched tumors (concordance rate 93%).
CONCLUSIONS: BRAF, RAS and TERT mutations are highly prevalent in metastatic DTC and are concordant between primary and metastatic DTC. This high concordance suggests that primary tumors may reflect the key somatic alterations in matched metastatic DTC. Frequent coexistent TERT promoter and BRAF or RAS mutations in metastatic DTC also suggests its important role in the progression of DTC.

PMID: 26971368 [PubMed - as supplied by publisher]

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