Clofarabine increases the eradication of minimal residual disease of primary B-precursor acute lymphoblastic leukemia compared to high-dose cytarabine without improvement of outcome. Results from the randomized clinical trial 08-09 of the Cooperative Acute Lymphoblastic Leukemia Study Group
Gabriele Escherich,
Udo zur Stadt,
Arndt Borkhardt,
Dagmar Dilloo,
Jörg Faber,
Tobias Feuchtinger,
Thomas Imschweiler,
Norbert Jorch,
Arnulf Pekrun,
Irene Schmid,
Franziska Schramm,
Michael Spohn,
Martin Zimmermann,
Martin A Horstmann
Affiliations
Gabriele Escherich
Clinic of Pediatric Hematology and Oncology, University Medical Center Hamburg-Eppendorf, Hamburg
Udo zur Stadt
Clinic of Pediatric Hematology and Oncology, University Medical Center Hamburg-Eppendorf, Hamburg
Arndt Borkhardt
Department of Pediatric Oncology, Hematology and Clinical Immunology, Medical Faculty Duesseldorf, Duesseldorf
Dagmar Dilloo
Department of Pediatric Hematology/Oncology, University Hospital Bonn, Bonn
Jörg Faber
Department of Pediatric Hematology/Oncology, University Hospital Mainz, Mainz
Tobias Feuchtinger
Dr. von Hauner Children's Hospital, Ludwig Maximilian University, Munich
Thomas Imschweiler
Department of Pediatric Hematology and Oncology, Helios Hospital, Krefeld
Norbert Jorch
Department of Pediatric Hematology and Oncology, Protestant Hospital of Bethel Foundation, Bielefeld
Arnulf Pekrun
Department of Pediatric Hematology and Oncology, Hospital Bremen-Mitte
Irene Schmid
Dr. von Hauner Children's Hospital, Ludwig Maximilian University, Munich
Franziska Schramm
Clinic of Pediatric Hematology and Oncology, University Medical Center Hamburg-Eppendorf, Hamburg
Michael Spohn
Clinic of Pediatric Hematology and Oncology, University Medical Center Hamburg-Eppendorf, Hamburg, Germany; Research Institute Children’s Cancer Center Hamburg, Germany; Bioinformatics Core Unit, University Medical Center Hamburg
Martin Zimmermann
Department of Pediatric Hematology and Oncology, Medical School Hannover, Hannover
Martin A Horstmann
Clinic of Pediatric Hematology and Oncology, University Medical Center Hamburg-Eppendorf, Hamburg, Germany; Research Institute Children’s Cancer Center Hamburg
Novel treatment strategies are needed to improve cure for all children with acute lymphoblastic leukemia (ALL). To this end, we investigated the therapeutic potential of clofarabine in primary ALL in trial CoALL 08-09 (clinicaltrials gov. identifier: NCT01228331). The primary study objective was the minimal residual disease (MRD)- based comparative assessment of cytotoxic efficacies of clofarabine 5x40 mg/m2 versus high-dose cytarabine (HIDAC) 4x3g/m2, both in combination with PEG-ASP 2,500 IU/m2 as randomized intervention in early consolidation. The secondary objective was an outcome analysis focused on treatment arm dependence and MRD after randomized intervention. In B-cell precursor (BCP)-ALL, eradication of MRD was more profound after clofarabine compared to cytarabine, with 93 versus 79 of 143 randomized patients per arm reaching MRD-negativity (c2 test P=0.03, leftsided P [Fisher’s exact test]=0.04). MRD status of BCP-ALL after randomized intervention maintained its prognostic relevance, with a significant impact on event-free survival (EFS) and relapse rate. However, no difference in outcome regarding EFS and overall survival (OS) between randomized courses was observed (5-year EFS: clofarabine 85.7, SE=4.1 vs. HIDAC 84.8, SE=4.7 [P=0.96]; OS: 95.7, SE=1.9 vs. 92.2, SE=3.2 [P=0.59]), independent of covariates or overall risk strata. Severe toxicities between randomized and subsequent treatment elements were also without significant difference. In conclusion, clofarabine/PEG-ASP is effective and safe, but greater cytotoxic efficacy of clofarabine compared to HIDAC did not translate into improved outcomes indicating a lack of surrogacy of post-intervention MRD at the trial level as opposed to the patient level, which hampers a broader implementation of this regimen in the frontline treatment of ALL.