For example, vandetanib showed a greater effect in CCDC6-RET fusion tumors compared with KIF5B-RET (57). However, the adverse effects of non-selective RET inhibitors observed in all treated tumors due to their off-target side effects are responsible for high discontinuation and dose reduction rates (e.g., 12% and 35% for vandetanib and 16% and 79% for cabozantinib when used as thyroid cancer treatments, respectively) (57). Here, RET is linked to thyroid cancer.