Clinical trial in patients with metastatic colorectal Cancer to evaluate the response of removable liver metastases after treatment with Cetuximab (Erbitux).

Primary objectives: To describe the histological response to Erbitux based chemotherapy in all excised liver metastases.
Primary endpoints: Pathological response will be assessed by pathologic evaluation of liver metastases, which will be performed centrally, and the degree of tumor regression. This evaluation will be performed according to Method Mandard in all the excised liver metastases, according to the following grades:1.TRG1, absence of residual cancer and large amount of fibrosis 2.TRG2, rare residual cancer cells scattered throughout the fibrosis 3.TRG3, more residual tumor cells but fibrosis predominates; 4.TRG4, residual cancer cells predominate over fibrosis; and 5.TRG5, no signs of regression.
Pathological response will be grouped as:
1.Major Histological Tumor Response (MjHR) including TRG1 and TRG22.Partial Histological Tumor Response (PHR) for TRG3 3.Non response (NHR) for TRG4 and TRG5 (3).