DISEASE CHARACTERISTICS:

Inclusion criteria:

• Diagnosis of B-cell chronic lymphocytic leukemia (B-CLL)

• Disease in complete or partial remission after completion of 4-6 courses of second-line cytoreductive therapy no less than 90 days and no more than 150 days ago

  • Second-line cytoreductive therapy must comprise 1 of the following regimens:

    • Fludarabine phosphate alone (F)
    • Fludarabine phosphate and cyclophosphamide (FC)
    • Fludarabine phosphate, cyclophosphamide, and rituximab (FCR)
    • Bendamustine hydrochloride alone (B)
    • Bendamustine hydrochloride and rituximab chemotherapy (BR)

• Complete minimal residual disease response defined by the following:

  • At least negativity of 4-color-cytometry and/or even PCR-amplifiable clonal CDR III rearrangement of the IgV_H

    • For PCR analysis, blood sample need to be taken at beginning or during second-line cytoreductive therapy before achievement of a clinical complete remission
• Disease not refractory to first-line F/FC/FCR/B/BR if received such therapy

Exclusion criteria:

• Presence of bulky lymph nodes (> 5 cm) after second-line F/FC/FCR/B/BR
• Clinically apparent autoimmune cytopenia (i.e., autoimmune hemolytic anemia, autoimmune thrombocytopenia, or pure red cell aplasia)
• CNS involvement with B-CLL

PATIENT CHARACTERISTICS:

Inclusion criteria:

• ECOG performance status 0-1
• ANC ≥ 1,500/µL
• Platelets ≥ 50,000/µL
• Creatinine ≤ 1.5 times the upper normal limit (ULN)
• Conjugated bilirubin ≤ 2 times ULN
• Thyroid function normal
• Not pregnant or nursing
• Fertile patients must use effective contraception

Exclusion criteria:

• Severe infection during second-line treatment with F/FC/FCR/B/BR, meeting any 1 of the following criteria:

  • Any episode of NCI grade 4 infection
  • More than 1 episode of NCI grade 3 infection
• Medical condition requiring long-term use of oral corticosteroids for more than 1 month
• Active bacterial, viral, or fungal infection
• HIV, hepatitis B virus, and/or hepatitis C virus-positive serum status

• Concurrent severe diseases that exclude the administration of protocol therapy, including any of the following:

  • NYHA class III-IV heart insufficiency
  • Severe chronic obstructive lung disease with hypoxemia
  • Severe ischemic cardiac disease
• Active secondary malignancy other than B-CLL prior to the study
• Known hypersensitivity or anaphylactic reaction against murine proteins or one of the drug components

PRIOR CONCURRENT THERAPY:

• See Disease Characteristics
• No more than 2 prior chemotherapies, including F/FC/FCR/B/BR therapy
• No more than 1 pretreatment (before second-line therapy) with chlorambucil or F/FC/FCR/B/BR
• No chemotherapy or radiotherapy for any neoplastic disease other than B-CLL prior to the study