RATIONALE: Drugs used in chemotherapy use different ways to stop tumor cells from dividing so they stop growing or die. Combining more than one drug may kill more tumor cells.

PURPOSE: Phase II trial to study the effectiveness of combination chemotherapy in treating children who have relapsed or refractory acute lymphocytic leukemia.

OBJECTIVES: I. Evaluate the complete response rate to combination fludarabine, idarubicin, and cytarabine in children with relapsed or refractory acute lymphocytic leukemia. II. Evaluate the safety and tolerance of this treatment in these patients. III. Evaluate the time to progression, disease free survival, and overall survival of these patients.

OUTLINE: This is an open label, multicenter study. Patients receive idarubicin IV over 1 hour on days 1-3. Fludarabine IV is administered over 30 minutes on days 1-5. Cytarabine IV is administered over 4 hours on days 1-5. If partial response is obtained, patients receive a second course of treatment. Patients receive a consolidation course in the absence of disease progression and unacceptable toxicity. Idarubicin IV is administered over 1 hour on days 1 and 2. Fludarabine IV is administered over 30 minutes, followed by cytarabine IV over 4 hours on days 1-5. Patients are followed every 3 months for 2 years or until death.

PROJECTED ACCRUAL: A total of 24-45 patients will be accrued for this study within 27 months.

• Drug: cytarabine
• Drug: fludarabine phosphate
• Drug: idarubicin

DISEASE CHARACTERISTICS: Cytologically diagnosed relapsed or refractory acute lymphocytic leukemia previously treated with front line therapy FAB L1 or L2 Bone marrow relapse either isolated or associated with CNS or testicular relapse Bone marrow blast cells greater than 10% No isolated CNS relapse

PATIENT CHARACTERISTICS: Age: Under 18 Performance status: WHO 0-2 Play-performance scale at least 60% Life expectancy: Not specified Hematopoietic: Not specified Hepatic: Bilirubin less than 2.5 times normal Renal: Creatinine less than 2.5 times normal Cardiovascular: No symptoms of cardiac failure No decline of ejection fraction by more than 20% of the lower limit of normal Shortening fraction at least 25% Other: No psychological, familial, sociological or geographical condition that would hamper compliance No uncontrolled infection

PRIOR CONCURRENT THERAPY: At least 6 months since prior autologous bone marrow transplantation No prior allogeneic bone marrow transplantation No concurrent treatment with other experimental drug