The reason for this study is to see if the study drug selpercatinib is safe and more effective compared to a standard treatment in participants with rearranged during transfection (RET)-mutant medullary thyroid cancer (MTC) that cannot be removed by surgery or has spread to other parts of the body. Participants who are assigned to the standard treatment and discontinue due to progressive disease have the option to potentially crossover to selpercatinib.
A Multicenter, Randomized, Open-label, Phase 3 Trial Comparing Selpercatinib to Physicians Choice of Cabozantinib or Vandetanib in Patients With Progressive, Advanced, Kinase Inhibitor Naïve, RET-Mutant Medullary Thyroid Cancer (LIBRETTO-531)
Adaptive sample size re-estimation will be performed at interim analysis. The sample size could be increased from approximately 250 to 400 depending on the results of interim analysis.