Ryder, Mabel

6087 Background: NTRK1-3 fusions, identified in pediatric radiation-associated thyroid cancers, are low frequency oncogenic drivers that can trigger constitutive activation of TrK1-3 tyrosine kinase domains with responsively heightened downstream signaling through RAS-MAPK, PI3K-AKT, and/or PLCγ-PKC. NTRK point mutations are rare and of largely uninvestigated oncogenic potential, but some appear oncogenic. Methods: Advanced thyroid cancer (TC) patients (pts) requiring systemic therapy at Mayo Clinic sites underwent tumor genetic interrogation using Foundation One analyses with the goal of informing salvage therapeutic strategies. In this IRB-approved study, data from pts with TCs bearing NTRK point mutations were retrospectively analyzed, as this occurrence was unexpected but potentially of prognostic and/or therapeutic relevance. Results: Five of 55 pts (9%) with advanced TCs subject to Foundation One tumor interrogation had NTRK1-3 point mutations (allele frequency, AF, 15-49%); none had fusions. All 5 tumors had microsatellite stability; 4/5 had low tumor mutation burden (2-5 mutations/megabase). NTRK mutations in 3 anaplastic TC (ATC) pts (15% prevalence) were: NTRK3 I749M (AF 15%; overall survival, OS, 15 mos), NTRK1 R744H (AF not available; OS 9.5 mos), and NTRK1 R583H (AF 20.1%; OS > 4.9 mos); NTRK2 S167Y (AF 49%; OS > 51 mos) or NTRK1 R6W (AF 42%; OS > 60 mos) were found in one papillary (PTC) and one Hürthle cell (HCC) TC pt respectively (summary table below). Conclusions: NTRK point mutations, but not fusions, were unexpectedly identified in 9% of assessed advanced TCs - but remarkably in 15% of ATCs. Mutated NTRKs, along with oncogenic p53 and TERT, may contribute to TC progression, especially in ATC, consequent to downstream activation of MAPK and PI3K-AKT pathways. We posit that NTRK point mutations may have therapeutic implications for treatment of refractory disease. [Table: see text]

Background: Historical anaplastic thyroid cancer (ATC) outcomes have been terrible, with a median survival of only five months and <20% one-year survival. Improved outcomes are now achieved with aggressive initial therapy in stages IVA and IVB disease, but patients with distant metastatic disease (stage IVC) still do poorly; improved therapies are sorely needed. Kinase inhibitors have emerged as promising agents in the therapy of advanced medullary and differentiated thyroid cancer, but there are limited data regarding the use of lenvatinib in ATC. The aim of this study was to delineate clinical outcomes in a series of patients with advanced ATC in response to lenvatinib therapy. Methods: A retrospective analysis was conducted involving all lenvatinib-treated Mayo Clinic ATC patients in 2015. Results: Of 28 distinct ATC patients seen in 2015, three (11%) with metastatic disease of ECOG performance status 2–3 were treated with lenvatinib. Two patients were male; age range at ATC diagnosis was 57–84 years. All three patients attained successful local control of their disease with surgery and/or combined chemoradiotherapy. Lenvatinib was offered as the second, third, or fourth line of therapy at the time of metastatic disease progression. Two patients incurred minor responses to therapy, with structural regression of distant metastatic tumor disease soon after starting lenvatinib treatment (at one to two months), while one patient achieved stable disease, but no Response Evaluation Criteria In Solid Tumors partial responses resulted. Overall survival after starting lenvatinib was two, six, and seven months. Fatigue and hypertension were prominent, and one patient developed pulmonary emboli while on lenvatinib. Conclusion: This initial single-institution experience suggests that lenvatinib may have some disease-modifying activity in metastatic ATC that is otherwise refractory to cytotoxic chemotherapy. Unfortunately, observed benefits were transient, and toxicities were prominent. Clinical trials are required to ascertain better the utility of lenvatinib in the management of advanced ATC.

Immune-related Adverse Events (irAEs) are the most significant toxicities associated with the use of checkpoint inhibitors, and result from disinhibition of the host’s immune homeostasis. The adverse effects experienced from immunotherapy are significantly different from those of chemotherapy and, to a lesser extent, targeted therapy. Early recognition and diagnosis of these toxicities is often challenging, but is critically important because of the potentially life-threatening nature and associated morbidity. Gastrointestinal, dermatologic, endocrine, and liver toxicities are the most commonly observed. Less commonly, the eyes, pancreas, kidneys, lungs, bone marrow, or nervous system may be affected. Although most irAEs may resolve with supportive care or discontinuation of drug, in severe cases, they may require hospitalization and immune suppressants, such as steroids, and/or may even cause death. The management of immune-related side effects requires a multidisciplinary approach.