Secondary objectives include monitoring progression-free and overall survival, assessing RET, EGFR, VEGFR andsomatostatin receptor expression in archival tumor tissue, assessing changes in DNA mutations in RET in tumor tissue vs germ line in PBMC and after treatment; assessing gene expression and gains/lossess of DNA in tumor tissue at baseline, during treatment and at the time of progression; establishment of pediatric MTC cell lines sensitive and resistant cells lines in vitro