Study of First-line Single-agent Panitumumab in Frail Elderly Patients With Advanced Wild Type K-RAS Colorectal Cancer

Inclusion Criteria: * Signed Inform Consent * Age \> 70 years. * Histologically documented metastatic colorectal cancer not candidate for surgical resection * Wild type K-RAS * Measurable disease by RECIST Criteria * Intermediate or High-risk group according to the Köhne Prognostic Classification * ECOG status \< 3 * Magnesium ≥ institutional lower limit of normal * frail elderly patients and or not candidates for chemotherapy: Frail elderly patients: Presence of one or more of the following criteria: * Dependence for one of the basic daily living activities (Katz Index) * Three or more comorbid conditions according Charlson scale and dependence for one of the instrumental activities of daily living (IADL) * Presence one or more of the following geriatric syndromes (age \> 85 years, fecal or urinary incontinence in the absence of stress, frequent falls, spontaneous bone fractures, neglect) Presence of one or more of the following criteria that make patients not candidates for chemotherapy: * neutrophils \< 2000/mm3 * platelets \< 100.000/mm3 * creatinine clearance \< 30 ml/min and bilirubin levels \> 1.5 x ULN * creatinine clearance \< 30 ml/min and AST or ALT levels \> 3 x UNL (if liver metastasis \> 5 x ULN) Exclusion Criteria: * Patients will be excluded from the study if they have received prior systemic therapy for the treatment of metastatic colorectal carcinoma or antiEGFR therapy, with the exception of adjuvant fluoropyrimidine-based chemotherapy given at least six months prior to enrolment or oxaliplatin at least 12 months prior to enrolment. * Systemic chemotherapy, hormonal therapy, immunotherapy or experimental or approved proteins/antibodies (eg, bevacizumab) ≤ 30 days before inclusion * Unresolved toxicities from prior systemic therapy that, in the opinion of the investigator, does not qualify the patient for inclusion * Patients cognitively impaired or with severe depression according mini mental state examination and geriatric depression scale. * Patients with central nervous system metastases, or those with significant cardiovascular disease, will also be excluded. * History of interstitial pneumonitis or pulmonary fibrosis or evidence of interstitial pneumonitis or pulmonary fibrosis on baseline chest CT scan * Treatment for systemic infection within 14 days before initiating study treatment * Radiotherapy \< 14 days prior to inclusion in the study. * Active inflammatory bowel disease or other bowel disease causing chronic diarrhoea (defined as \> 4 loose stools per day) * History of any medical condition that may increase the risks associated with study participation or may interfere with the interpretation of the study results * Known positive test for human immunodeficiency virus infection, hepatitis C virus, chronic active hepatitis B infection * subject allergic to the ingredients of the study medication or to Staphylococcus protein A * Any co-morbid disease that would increase risk of toxicity * Any investigational agent within 30 days before enrolment * Must not have had a major surgical procedure within 28 days of enrolment * Subject unwilling or unable to comply with study requirements