Rituximab in Pretreated Elderly or Unfit B-CLL Patients

Inclusion Criteria: * The diagnosis of CD20 positive chronic B lymphocytic leukemia (BCLL) confirmed by biopsy or flow-cytometry. * Previously treated patients with stage Rai I-IV and progressive disease (according to IWCLL 2008 guidelines). Active B-CLL is defined by at least one of the following: At least one of the disease related symptoms: * Constitutional symptoms: * Weight loss \>10% within the previous 6 months; * Fatigue (e.g., WHO performance status \>/=2); * Fever \>/=38C \>/=2 weeks without evidence of infection; * Night sweats for more than 1 month without evidence of infection. * Evidence of progressive marrow failure as manifested by development of, or worsening of, anemia and/or thrombocytopenia * Autoimmune hemolysis and/or thrombocytopenia poorly responsive to corticosteroid therapy. * Massive (i.e., \>/=6 cm bellow left costal margin) or progressive or symptomatic splenomegaly. * Massive lymphadenopathy or conglomerates (i.e., \>/=10 cm in largest diameter) or progressive or symptomatic lymphadenopathy. * Progressive lymphocytosis with an increase \>50% over a 2-month period or an anticipated doubling time of less than 6 months. In patients with initial blood lymphocyte counts of less than 30x10\^9/L LDT should not be used as a single parameter to define treatment indication. Marked hypogammaglobulinemia or the development of a monoclonal protein in the absence of any of the above criteria for active disease is not sufficient for protocol therapy. * Either of the following: * 18 years of age or older with impaired performance status (CIRS \> 6) and /or * 65 years of age or older with any performance status. * Signed informed consent form. Exclusion Criteria: * Intolerance to exogenous protein or known severe reaction to the administration of Rituximab. * Active infection. * Cancer radiotherapy, biological therapy or chemotherapy within 3 weeks prior to Study Day 1. * TBC or fungal infection within the past 6 months even if adequately controlled by treatment. * Severe organ deficiency preventing the participation in the study. * Major surgery, other than diagnostic surgery, within 4 weeks prior to Study Day 1. * Active peptic ulcer. * Inadequately controlled diabetes mellitus. * Suspected or confirmed B-CLL CNS disease. * Known to be HIV positive. * Difficult to control, uncooperative patients. * Allergic disorders in need of chronic glucocorticoid therapy. * Other oncological diseases requiring active treatment (except hormonal therapy). * Pregnancy and breastfeeding. * Patients of reproductive potential who are not using effective methods of contraception.