A B S T R A C T PurposeTo determine if alemtuzumab consolidation improves response rate and progression-free survival (PFS) after induction chemoimmunotherapy in previously untreated symptomatic patients with chronic lymphocytic leukemia. Patients and MethodsPatients (n ϭ 102) received fludarabine 25 mg/m 2 intravenously days 1 to 5 and rituximab 50 mg/m 2 day 1, 325 mg/m 2 day 3, and 375 mg/m 2 day 5 of cycle 1 and then 375 mg/m 2 day 1 of cycles 2 to 6; fludarabine plus rituximab (FR) administration was repeated every 28 days for six cycles. Three months after completion of FR, patients with stable disease or better response received subcutaneous alemtuzumab 3 mg day 1, 10 mg day 3, and 30 mg day 5 and then 30 mg three times per week for 5 weeks. ResultsOverall response (OR), complete response (CR), and partial response (PR) rates were 90%, 29%, and 61% after FR, respectively; 15% of patients were minimal residual disease (MRD) negative. Of 102 patients, 58 received alemtuzumab; 28 (61%) of 46 patients achieving PR after FR attained CR after alemtuzumab. By intent to treat (n ϭ 102), OR and CR rates were 90% and 57% after alemtuzumab, respectively; 42% of patients became MRD negative. With median follow-up of 36 months, median PFS was 36 months, 2-year PFS was 72%, and 2-year OS was 86%. In patients achieving CR after FR, alemtuzumab was associated with five deaths resulting from infection (viral and Listeria meningitis and Legionella, cytomegalovirus, and Pneumocystis pneumonias), which occurred up to 7 months after last therapy. The study was amended to exclude CR patients from receiving alemtuzumab. ConclusionAlemtuzumab consolidation improved CR and MRD-negative rates after FR induction but caused serious infections in patients who had already achieved CR after induction and did not improve 2-year PFS or survival.