The primary objective of the 2nd line studies is to determine, separately for each study, whether the addition of cetuximab to a polyCT schemes (FOLFOX or FOLFIRI), or to polyCT schemes plus bevacizumab, improves efficacy in terms of PFS.The secondary objectives of the 2nd line studies are to determine the ORR, the overall survival (OS) and the safety profile of the treatments administered.