T Regulatory Lymphocytes (Treg) Depletion for Cancer Treatment Efficacy and Safety Study

T regulatory lymphocytes were shown to be partly responsible for immune tolerance to cancer cells. In that respect these cells oppose to the mounting of an efficacious immune response needed to cure cancer. To treat advanced metastatic colorectal cancer, the investigators propose an immunotherapy consisting in autologous lymphocytes infusion depleted from T-regulatory cells, associated with a 5-day prior lymphoid-ablative chemotherapy associating cyclophosphamide (day 1 & 2) with fludarabine (day 1 to 5). To administer treatment and monitor chemotherapy safety, patients will be hospitalized for 3 weeks until complete recovery from chemotherapy. Patients will then be followed-up ambulatory for 9 months during which time they will be assessed for tumor size with computed tomography (CT) - scan (primary criteria).