RET and medullary thyroid gland carcinoma: In the LIBRETTO-531 trial, the median PFS was not reached for selpercatinib-treated patients with RET-mutant MTC who were naïve to cabozantinib/vandetanib versus 16.8 months for those treated with cabozantinib/vandetanib; the HR (95% CI) for disease progression or death was 0.28 (0.16 and 0.48, p < 0.001).