A Direct Comparison of High Dose Cytarabine to Combination of Gemtuzumab and High Dose Cytarabine for Acute Myeloid Leukemia Patients in First Relapse Confirmed the Benefit of Gemtuzumab Based Regimens.

Abstract 2051

Poster Board II-28

Acute meyloid leukemia (AML) in first relapse is associated with a poor outcome when treated with standard dose cytarabine regimens and intermediate to high dose cytarabine (IHDAraC) is the current standard of care. During the last years, Gemtuzumab Ozogamycin (GO) has demonstrated a relevant clinical activity in relapsed and refractory AML. This antibody directed against CD33 is conjugated to calicheamycin that triggers apoptosis when hydrolyzed in the leukemic blasts. Combination regimen of GO are currently extensively studied in both frontline and advanced phase disease. Nevertheless, analysis of the litterature showed that only few data are available regarding a direct comparison of IHDAraC and IHDAraC+GO regimen. To this respect, we conduced a retrospective analysis of response (CR and CRi) and survival for patients with first relapse AML treated in our centre with either IHDAraC or IHDAraC+GO regimen. A total of 84 patients were included in the analysis: 28 were induced in the IHDAraC+GO group (mean GO dose: 6mg/m2, range:[3-9], including 82% of combination with anthracyclines or etoposide) and 56 in the IHDAraC group (including 57% of combination with other agents, mostly etoposide and anthracyclines). Patients characteristics were comparable between the IHDAraC+GO group and the control group in terms of median age (51y vs 49y), Performance Status at relapse (1 vs 1), median time to relapse (221 days vs 280 days), cytogenetic risk group clustering and previous allogeneic transplantation in first CR (21% vs 16%). Median Follow-up was 24 months. Univariate analysis showed that IHDAraC+GO induction, as compared with IHDAraC, was associated with a better response rate (68% vs 48%, p=0.08), a lower relapse rate (31% vs 66%, p=0.02), a better Overall Survival (median 35 months vs 19 months, p=0.02) and a better Event Free Survival (median Not Reached vs 10 months, p=0.02). Of note, the better response rate in the IHDAraC+GO group allowed to bring more patients to allogeneic transplantation in second CR (33% vs 16% respectively, p=0.08).Multivariate analysis using logistic regression method for response evaluation and Cox model for survival showed that treatment in the IHDAraC+GO group was an independent prognosis factor with a favorable impact on both response (HR:2.8, 95%CI:[1.1-7.7], p=0.048) and Overall Survival (HR:1.9, 95%CI:[1.1-3.4], p=0.047). It is already known that combination of IHDAraC and GO could give good results for advanced phase AML patients but, to our knowledge, this report is the first that directly compared the results of IHDAraC+GO with the current standard of care regimen on an homogeneous sample of patients in first relapse. This report also underline the importance of a prospective comparison in order to define the best combination therapy.