Real-world external control arm for the single-arm LIBRETTO-001 trial of selpercatinib in RET-mutation-positive medullary thyroid cancer: RECALIB-RET

BACKGROUND: The single-arm phase I/II LIBRETTO-001 trial demonstrated durable efficacy with selpercatinib in patients with rearranged during transfection (RET)-mutation-positive medullary thyroid cancer (MTC). RECALIB-RET compared effectiveness outcomes using a real-world external control (EC) arm of patients with RET-mutation-positive MTC treated with standard of care (SoC) versus selpercatinib (LIBRETTO-001). PATIENTS AND METHODS: In this retrospective study, the selpercatinib arm comprised first-line (1L) or second-and-later-line (≥2L) patients from LIBRETTO-001. The EC arm comprised SoC-treated patients, pooled across (i) the French ENDOCAN-TUTHYREF (Refractory Thyroid Tumours) database (1L and ≥2L); (ii) a chart review of European patient medical records (1L and ≥2L) and (iii) a published United States chart review (≥2L). Index treatment was cabozantinib or vandetanib (1L) and any SoC (≥2L; including multikinase inhibitor, chemotherapy or immunotherapy). The primary endpoint was progression-free survival (PFS). The safety profile of SoC in the EC arm was a secondary endpoint. Propensity score matching (PSM) balanced baseline characteristics between treatment arms. RESULTS: Baseline characteristics of the 1L selpercatinib (n = 116) and EC (n = 107) arms were balanced; PSM reduced the sample size by