NTRK and RET fusion-directed therapy in pediatric thyroid cancer yields a tumor response and radioiodine uptake

J Clin Invest. 2021 Sep 15;131(18):e144847. doi: 10.1172/JCI144847.


BACKGROUNDMolecular characterization in pediatric papillary thyroid cancer (PTC), distinct from adult PTC, is important for developing molecularly targeted therapies for progressive radioiodine-refractory (131I-refractory) PTC.METHODSPTC samples from 106 pediatric patients (age range: 4.3-19.8 years; n = 84 girls, n = 22 boys) who were admitted to SNUH (January 1983-March 2020) were available for genomic profiling. Previous transcriptomic data from 125 adult PTC samples were used for comparison.RESULTSWe identified genetic drivers in 80 tumors: 31 with fusion oncogenes (RET in 21 patients, ALK in 6 patients, and NTRK1/3 in 4 patients); 47 with point mutations (BRAFV600E in 41 patients, TERTC228T in 2 patients [1 of whom had a coexisting BRAFV600E], and DICER1 variants in 5 patients); and 2 with amplifications. Fusion oncogene PTCs, which are predominantly detected in younger patients, were at a more advanced stage and showed more recurrent or persistent disease compared with BRAFV600E PTCs, which are detected mostly in adolescents. Pediatric fusion PTCs (in patients <10 years of age) had lower expression of thyroid differentiation genes, including SLC5A5, than did adult fusion PTCs. Two girls with progressive 131I-refractory lung metastases harboring a TPR-NTRK1 or CCDC6-RET fusion oncogene received fusion-targeted therapy; larotrectinib and selpercatinib decreased the size of the tumor and restored 125I radioiodine uptake. The girl with the CCDC6-RET fusion oncogene received 131I therapy combined with selpercatinib, resulting in a tumor response. In vitro 125I uptake and 131I clonogenic assays showed that larotrectinib inhibited tumor growth and restored radioiodine avidity.CONCLUSIONSIn pediatric patients with fusion oncogene PTC who have 131I-refractory advanced disease, selective fusion-directed therapy may restore radioiodine avidity and lead to a dramatic tumor response, underscoring the importance of molecular testing in pediatric patients with PTC.FUNDINGThe Ministry of Science, ICT and Future Planning (NRF-2016R1A2B4012417 and 2019R1A2C2084332); the Korean Ministry of Health and Welfare (H14C1277); the Ministry of Education (2020R1A6A1A03047972); and the SNUH Research Fund (04-2015-0830).TRIAL REGISTRATIONTwo patients received fusion-targeted therapy with larotrectinib (NCT02576431; NAVIGATE) or selpercatinib (LOXO-RET-18018).

Keywords: Cancer; Endocrinology; Oncogenes; Oncology; Thyroid disease.

Publication types

  • Research Support, Non-U.S. Gov't

MeSH terms

  • Adolescent
  • Age Factors
  • Child
  • Child, Preschool
  • Combined Modality Therapy
  • Female
  • Humans
  • Iodine Radioisotopes / pharmacokinetics
  • Iodine Radioisotopes / therapeutic use
  • Male
  • Molecular Targeted Therapy / methods*
  • Oncogene Proteins, Fusion / genetics
  • Proto-Oncogene Proteins c-ret / antagonists & inhibitors
  • Proto-Oncogene Proteins c-ret / genetics*
  • Pyrazoles / therapeutic use
  • Pyridines / therapeutic use
  • Pyrimidines / therapeutic use
  • Radiopharmaceuticals / pharmacokinetics
  • Radiopharmaceuticals / therapeutic use
  • Receptor, trkA / antagonists & inhibitors
  • Receptor, trkA / genetics*
  • Thyroid Cancer, Papillary / genetics*
  • Thyroid Cancer, Papillary / radiotherapy
  • Thyroid Cancer, Papillary / therapy*
  • Thyroid Neoplasms / genetics*
  • Thyroid Neoplasms / radiotherapy
  • Thyroid Neoplasms / therapy*
  • Transcriptome
  • Young Adult


  • Iodine Radioisotopes
  • Iodine-131
  • NTRK1 protein, human
  • Oncogene Proteins, Fusion
  • Pyrazoles
  • Pyridines
  • Pyrimidines
  • Radiopharmaceuticals
  • selpercatinib
  • Proto-Oncogene Proteins c-ret
  • RET protein, human
  • Receptor, trkA
  • Iodine-125
  • larotrectinib

Associated data

  • ClinicalTrials.gov/NCT02576431