Therapy Optimisation for the Treatment of Hairy Cell Leukemia

Inclusion Criteria:

• Patients with histologically verified hairy cell leukemia

• Presence of hairy cells in the bone marrow and peripheral blood detected by positiveTRAP staining and / or co expression if cell surface antigens cluster ofdifferentiation (CD) 19/CD25 or CD19/CD103 (b-ly7)

• No previous cytostatic treatment (splenectomy or interferon treatment are allowed)

• Need for treatment

• Age at least 18 years old

• General state of health according to WHO 0-2

• Current histology, not older than 6 months

• Written consent by patient

Exclusion Criteria:

• Patients not fulfilling inclusion criteria above

• Hairy cell leukemia variants (HCL-V): presence of lymphoid cells in bone marrow and / or peripheral blood, which have an intermediate morphology between hairy cells andprolymphocytes (negative TRAP staining and co- expression of CD19/CD103 without CD25

• Pretreatment with purine analogues or other chemotherapeutics

• Concomitant corticosteroid therapy

• Severe dysfunction of the heart (NYHA III or IV), the lung (WHO-Grade III or IV),the liver, except due to lymphoma (bilirubin > 2 mg/dl, alkaline phosphatase,glutamate-oxalacetate transaminase and glutamate-pyruvate transaminase > 2 x upperlimit of normal), the kidneys (creatinin > 2 mg/dl or creatinine clearance < 50ml/min), central nervous system diseases including psychoses.

• Proven HIV infection

• Active Hepatitis

• Other florid infections

• Anamnesis / diagnosis of other malignant disease (other than non-melanoma associatedskin tumours or stage 0 in situ carcinoma of the cervix)

• Pregnant or lactating women