Prognostic factors for response to second induction course in patients showing persistent disease after first course of standard induction chemotherapy for de novo acute myeloid leukemia (AML)

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7056 Background: Standard induction chemotherapy for AML consists of cytarabine plus daunorubicin or idarubicin (‘7+3' regimen). For patients showing persistent leukemia after first induction course (IND1) of the induction, usual practice is to give a second course (IND2) of similar regimen (‘7+3' or 5+2'). This strategy, however, has not been well evaluated. We investigated prognostic factors for response to IND2. Methods: We performed a retrospective study in 110 patients with de novo AML. All patients received cytarabine (100 or 200 mg/m2/d) for 7 days plus daunorubicin (45–60 mg/m2/d) or idarubicin (12 mg/m2/d) for 3 days as IND1. Patients who showed persistent leukemia after IND1 were given the same doses and drugs as ‘5+2’ (n = 85) or ‘7+3’ (n = 25) for IND2. We collected the clinico-pathologic data of the patients at diagnosis and at IND2, and analyzed prognostic factors for response to IND2. Results: Sixty-one (55.5%) of 110 patients, who received IND2, achieved complete remission (CR). The causes of treatment failure were resistant disease in 35, complication of aplasia in 8, and indeterminated in 6. Five-year probabilities of overall and relapse-free survival were 25% and 21%, respectively. Multivariate analysis demonstrated that cellularity at interim BM biopsy > 30% (p = 0.015), blast percentage at interim BM aspiration > 30% (p = 0.031), presence of circulating blasts at IND2 (p = 0.011), and unfavorable chromosomal abnormalities (p = 0.014) were independent risk factors for failure to induce CR. The CR rates were significantly different according to the number of the risk factors: 73% for 0–1 factor, 48% for 2 factors, and 11% for 3–4 factors (p< 0.001). Conclusions: We identified 4 independent poor risk factors for CR in patients who showed persistent disease after standard induction chemotherapy and who received similar second induction course. Other treatment strategies such as high-dose cytarabine rather than standard regimens seem to be needed for the patients with 3–4 risk factors before IND2. No significant financial relationships to disclose.