D898_E901 RET Deletion Is Oncogenic, Responds to Selpercatinib, and Treatment Resistance Can Arise Via RET-Independent Mechanisms.

deletion is a gain-of-function mutation and responds to tyrosine kinase inhibitors in MTC. RET Δ898-901 mutant is sensitive to selpercatinib and vandetanib, and acquired resistance to selpercatinib may develop via RET-independent mechanisms.