 - for patients not prescribed with vandetanib: negative RET mutation status must be determined from a tumour sample obtained within 18 months prior to enrollment. It is strongly recommended that a tissue sample obtained within 6 months prior to enrolment is used. 7. For patients newly prescribed vandetanib 300 mg, the prescription should be issued according to marketing authorisation and following the vandetanib Summary of Product Characteristics SmPC Appendix B. The starting dose could be reduced to 200 mg in patients with moderate renal impairment 