Impact Of The Early Intensification Of Induction Chemotherapy On Complete Remission and Survival Rates For De Novo Adult Acute Myeloid Leukemia

The successful induction chemotherapy of acute myeloid leukemia (AML) depends on the ability to achieve complete remission (CR) and to maintain remission status as long as possible. Approach to improve the rate of CR includes the intensification of induction chemotherapy for AML. The primary goal of this study was to evaluate and compare the long-term outcomes between remission induction therapy with and without early intensification added to the standard 3+7 remission induction regimen.

A retrospective analysis was performed on de novo AML patients diagnosed and treated at Catholic Blood and Marrow Transplantation Center between January 2001 and December 2010. Six hundred forty-one adults of ages between 16 and 60 were included, all of whom received induction chemotherapy starting with 3 days of idarubicin and 7 days of cytarabine or behenoyl cytarabine (BHAC). Cases with t(9;22) and t(15;17) were excluded. Bone marrow (BM) aspiration study was assessed on day 7 of induction in all patients. Factors which were considered for early intensification of induction were the presence of ≥ 5% BM blasts, patient performance, and other high risk clinical characteristics, such as karyotype. Groups according to early intensification on days 8 to 10 of induction were as followings: no intensification (3+7), n=156; cytarabine or BHAC for 3 days (3+10), n=233; addition of idarubicin for 2 days to 3+10 regimen (5+10), n=252. After a median duration of 5.5 months (3.3-19.0) from diagnosis, 479 patients underwent stem cell transplantation (autologous [auto-SCT], n=144; allogeneic [allo-SCT], n=335). Conditioning regimen for auto-SCT consisted of fractionated total body irradiation (TBI), melphalan, and cytarabine, whereas 83% (n=278) of patients with allo-SCT received myeloablative conditioning, of which was mostly TBI-based regimen (92%). Donors were matched sibling (n=213), matched unrelated (n=63), mismatched unrelated (n=39), and haploidentical related (n=20).

The median age at diagnosis was 39 years (16-60). Mean values of BM blast % on day 7 of induction was 3.5 in 3+7 group, 7.9 in 3+10, and 33.6 in 5+10 (p=<0.0001), while no significant difference in the proportion of adverse karyotype was shown (11.7% vs. 12.8%, p=0.804). After first induction (3+7, n=165; 3+10/5+10, n=465), the CR/CRi rate was significantly higher in 3+10/5+10 versus 3+7 (78.1% vs. 69.2%, p=0.023), while the rate for death in aplasia was lower (4.3% vs. 9.6%, p=0.013). After re-induction with various regimens, the CR/CRi rate was still significantly higher in intensified group (p=0.012). The relapse rates between the groups in 536 patients achieving CR (83.6%), however, was not significantly different (8.9% vs. 9.9%, p=0.737). SCT was performed at CR1 (n=459), CR2 (n=10), or relapsed/refractory status (n=10). Patients with auto-SCT mostly had better/intermediate cytogenetic risk (96%) at diagnosis, while 12% of allo-SCT had poor karyotype. After the median follow-up duration of 60.2 months (2.2-143.5), the median overall survival (OS) in all patients (n=641) was 65.6 months. The 5-year disease-free survival (DFS) of patients with auto- and allo-SCT was 58.4±4.2 and 64.9±2.7, respectively. Of 334 patients receiving allo-SCT, the 5-year DFS was significantly higher in patients achieving CR1 (n=299) after first induction therapy (p<0.0001), in whom 75% of them had early intensification. Other factors with significant impact on DFS after allo-SCT (n=334) were karyotype at diagnosis (p=0.032) and donor type (HLA-matched vs. HLA-mismatched sibling or unrelated, 58.1%±3.8 vs. 45.1±8.0, p=0.016). The significances were confirmed in multivariate analysis, which demonstrated that achieving CR1 after first induction regimen and its maintenance until SCT was the most powerful predictor for DFS after allo-SCT (67.1±2.9 vs. 34.6±7.8, p=<0.0001). When all patients were analyzed, according to induction intensification, a statistically significant benefit in 10-year OS was observed in 5+10 intensified group (44.8% vs. 52.9%, p=0.032).

Our results suggest possible benefit of examining day 7 BM aspiration for the strategy of early intensification of induction chemotherapy for adult AML patients and our intensification doses can be safely added with high efficacy in the achievement of CR1 compared to 3+7 standard regimen, and may have affected for better DFS after allo-SCT.

Kim:BMS: Consultancy, Honoraria, Membership on an entity’s Board of Directors or advisory committees, Research Funding; Novartis: Consultancy, Honoraria, Membership on an entity’s Board of Directors or advisory committees, Research Funding; Pfizer: Consultancy, Honoraria, Membership on an entity’s Board of Directors or advisory committees, Research Funding.