Effectiveness of Peripheral Blood (PB) Molecular Monitoring by Quantitative RT-PCR (Q-PCR) in Phase II Acute Promyelocytic Leukemia (APL) Trial J0422

Abstract Bone marrow (BM) is the accepted source for monitoring post-therapy minimal residual disease (MRD) in APL. PB is easier and less painful to obtain but variable, sometimes contradictory evidence has been presented for its efficacy in MRD monitoring. In this study, PB vs BM monitoring, as well as conventional, qualitative RT-PCR (C-PCR) vs Q-PCR were directly and prospectively compared for their effectiveness as part of an intensive MRD monitoring schedule applied as a safety measure to an investigative Phase II trial (J0422) designed to test the efficacy of minimizing chemotherapy exposure and treatment duration. This trial consisted of one cycle of induction with all-trans retinoic acid (ATRA) and daunorubicin, followed by consolidation with single-agent arsenic trioxide (ATO), followed by a maintenance phase of intermittent ATRA alone or with 6-mercaptopurine and methotrexate for patients (pts) with a presenting white blood cell count (WBC) of >10,000 WBC/uL. The MRD monitoring schedule was as follows: BM and PB after the induction and consolidation treatment modules (modules 1 & 2), then, PB every month and BM every 3 months during 2 years of maintenance therapy. C-PCR and Q-PCR were performed according to published procedures for monitoring the APL-specific fusion gene PML-RARα by the BIOMED-1 Concerted Action and the North American Cooperative Oncology Groups, respectively. Criteria for positive assays were: C-PCR, confirmed visualization of an appropriate-sized gel band after conventional, double-nested PCR amplification; Q-PCR, demonstration of a CT value 10,000 (7 pts), suggesting an association of pretreatment WBC with a difference in the initial dynamics of treatment response. After module-2 consolidation, 0 pts were positive by C-PCR and 3 by Q-PCR (1 BM & PB, 1 BM-only, 1 PB-only). During maintenance at the 3 mo shared BM/PB checkpoints, 0 C-PCR and 5/114 Q-PCR assays were positive (2 BM & PB, 1 BM-only, 2 PB-only), distributed among 3 pts. At monthly PB-only checkpoints, an additional 12/252 assays were positive by Q-PCR, none in a progressive pattern suggestive of impending molecular relapse. Overall, 1 – 3 Q-PCR assays were positive in 9 patients during the maintenance and follow-up periods. Among 8 pts who completed 24 mo maintenance, only 1/6 positive Q-PCR assays occurred at >12 mo, suggesting continued reduction of MRD during first 12 mo of maintenance therapy. No C-PCR assays were positive beyond module-1. In 1 exceptional pt, excluded from the above maintenance analysis, the Q-PCR assays became recurrently positive in BM and/or PB after 6 mo maintenance at a level below the criterion for molecular relapse (normalized quotient relative to the housekeeping gene GAPDH, NQGAPDH, ≥10−5). After 18 mo, the C-PCR became repeatedly positive in PB but not BM with Q-PCRs positive (2 BM & PB, 1 PB-only at shared checkpoints) in the NQGAPDH 4×10−7 to 4×10−6 range, which was associated with relapse in the central nervous system but not the BM. These results indicate that molecular monitoring of PB or BM was equally effective in detecting MRD and that Q-PCR was a more critical measure of MRD than C-PCR on protocol J0422 after single-cycle ATO-based consolidation therapy. The results further suggest that PB monitoring may be more effective in detecting extramedullary relapse, a relatively increasing cause of disease relapse with improved overall therapy for APL

Minimizing Therapy for Patients with Acute Promyelocytic Leukemia: Efficacy of Single Cycle of Arsenic-Based Consolidation Therapy

Abstract Current strategies for the treatment of patients with acute promyelocytic leukemia provide event-free survival of 75 – 85%. Most multicenter studies have used large doses of anthracyclines and multiple cycles of treatment. Based on the extremely high efficacy of arsenic trioxide (ATO) as single agent re-induction therapy, we conducted a Phase II study which minimized anthracycline exposure and treatment duration in newly diagnosed APL patients. The study design was modified from a previous trial which successfully used a single cycle of consolidation chemotherapy (Am. J. Heme.2005;79:119–27). All patients received ATRA for 60 days with daunorubicin (DRN, 60 mg/m2/dose IV) on days 4, 6, 8 unless urgent cytoreduction was required. Consolidation, begun between days 60 and 67, consisted of cytarabine 0.667 gm/m2/day IV continuous infusion days 1 – 3, DRN 60 mg/m2/dose IV days 1 – 3, and ATO 0.15 mg/kg IV for 30 doses, administered five days per week beginning on day 8 of consolidation on an outpatient basis. A second module of ATO was planned for patients with a positive qualitative rt-PCR for PML-RARα (sensitivity 1/10000) following recovery from consolidation. Patients whose initial WBC was 20% in three patients to EF values of 20 – 30%, with biopsyproven anthracycline-induced cardiomyopathy documented by biopsy in two patients, indicating possible cardiac sensitization by ATRA to anthracycline. These data suggest that the inclusion of ATO in primary APL management may allow further minimization of conventional cytotoxic chemotherapy without compromising cure rates, and demonstrate the critical need to determine the minimum curative therapy for APL patients. Series Total anthracycline dose administered (mg/m2 DRN equivalent)a Age (median) Sanz Relapse risk: High (percent) Follow- up (years, median) Overall survival Disease- Free Survival Event- Free Survival a Daunorubicin= 1. Mitoxantrone = 2.5. Idarubicin = 5. b nr indicates not reported c Selected based on Sanz risk score 90.5 92.9 83.6 Current 360 50 32 1.8 86 87 77 C9710 ATO arm 500 nrb 24 2.4 82 84 nr PETHEMA LPA99 525 – 625c 37 25 5.4 APL2000 Ara-C arm 495 43 46 5.2 90.5 nr 85.

Single Cycle of Arsenic Trioxide–Based Consolidation Chemotherapy Spares Anthracycline Exposure in the Primary Management of Acute Promyelocytic Leukemia

PURPOSE Event-free survival following all-trans-retinoic acid (ATRA) -based therapy for acute promyelocytic leukemia (APL) averages 70% at 5 years. While arsenic trioxide (ATO) can induce remissions in 95% of relapsed patients, few studies have addressed the integration of ATO into the primary management of APL. This study examines the efficacy of a single cycle of ATO-based consolidation therapy in a treatment regimen designed to decrease exposure to other cytotoxic agents. PATIENTS AND METHODS After induction with ATRA and daunorubicin (DRN), untreated patients with APL received 3 days of cytarabine and DRN followed by 30 doses of ATO beginning on day 8. Molecular remitters received 2 years of risk-based maintenance therapy. Results Forty-one of 45 patients receiving induction therapy achieved remission; four patients died (one before treatment was initiated). Thirty-seven patients received consolidation and maintenance; of these one patient relapsed (CNS) and one died in remission during maintenance therapy (hepatic sickle cell crisis). With a median follow-up of 2.7 years, estimated disease-free survival was 90%; overall survival for all patients was 88%. Despite a total anthracycline dose of only 360 mg/m(2), cardiac ejection fraction decreased by > or = 20% in 20% of patients. CONCLUSION These data, combined with other recent studies using ATO in the primary management of APL, demonstrate the important role that ATO can play in the primary management of this curable disease. Future studies should continue to focus on reducing the toxicity of treatment without increasing the relapse rate

Treatment-influenced associations of PML-RARα mutations, FLT3 mutations, and additional chromosome abnormalities in relapsed acute promyelocytic leukemia

Mutations in the all-trans retinoic acid (ATRA)-targeted ligand binding domain of PML-RARα (PRα/LBD+) have been implicated in the passive selection of ATRA-resistant acute promyelocytic leukemia clones leading to disease relapse.Among 45 relapse patients from the ATRA/chemotherapy arm of intergroup protocol C9710, 18 patients harbored PRα/LBD+ (40%), 7 of whom (39%) relapsed Off-ATRA selection pressure, suggesting a possible active role of PRα/LBD+. Of 41 relapse patients coanalyzed, 15 (37%) had FMS-related tyrosine kinase 3 internal tandem duplication mutations (FLT3-ITD+), which were differentially associated with PRα/LBD+ depending on ATRA treatment status at relapse: positively, On-ATRA; negatively, Off-ATRA. Thirteen of 21 patients (62%) had additional chromosome abnormalities (ACAs); all coanalyzed PRα/LBD mutant patients who relapsed off-ATRA (n = 5) had associated ACA. After relapse Off-ATRA, ACA and FLT3-ITD+ were negatively associated and were oppositely associated with presenting white blood count and PML-RARα type: ACA, low, L-isoform; FLT3-ITD+, high, S-isoform. These exploratory results suggest that differing PRα/LBD+ activities may interact with FLT3-ITD+ or ACA, that FLT3-ITD+ and ACA are associated with different intrinsic disease progression pathways manifest at relapse Off-ATRA, and that these different pathways may be short-circuited by ATRA-selectable defects at relapse On-ATRA. ACA and certain PRα/LBD + were also associated with reduced postrelapse survival. © 2012 by The American Society of Hematology

New Role for Granulocyte Colony-Stimulating Factor-Induced Extracellular Signal-Regulated Kinase 1/2 in Histone Modification and Retinoic Acid Receptor α Recruitment to Gene Promoters: Relevance to Acute Promyelocytic Leukemia Cell Differentiation ▿

The induction of the granulocytic differentiation of leukemic cells by all-trans retinoic acid (RA) has been a major breakthrough in terms of survival for acute promyelocytic leukemia (APL) patients. Here we highlight the synergism and the underlying novel mechanism between RA and the granulocyte colony-stimulating factor (G-CSF) to restore differentiation of RA-refractory APL blasts. First, we show that in RA-refractory APL cells (UF-1 cell line), PML-RA receptor alpha (RARα) is not released from target promoters in response to RA, resulting in the maintenance of chromatin repression. Consequently, RARα cannot be recruited, and the RA target genes are not activated. We then deciphered how the combination of G-CSF and RA successfully restored the activation of RA target genes to levels achieved in RA-sensitive APL cells. We demonstrate that G-CSF restores RARα recruitment to target gene promoters through the activation of the extracellular signal-regulated kinase (ERK)/mitogen-activated protein kinase (MAPK) pathway and the subsequent derepression of chromatin. Thus, combinatorial activation of cytokines and RARs potentiates transcriptional activity through epigenetic modifications induced by specific signaling pathways

Comprehensive mutational analysis of primary and relapse acute promyelocytic leukemia

Acute promyelocytic leukemia (APL) is a subtype of myeloid leukemia characterized by differentiation block at the promyelocyte stage. Besides the presence of chromosomal rearrangement t(15;17), leading to the formation of PML-RARA (promyelocytic leukemia-retinoic acid receptor alpha) fusion, other genetic alterations have also been implicated in APL. Here, we performed comprehensive mutational analysis of primary and relapse APL to identify somatic alterations, which cooperate with PML-RARA in the pathogenesis of APL. We explored the mutational landscape using whole-exome (n=12) and subsequent targeted sequencing of 398 genes in 153 primary and 69 relapse APL. Both primary and relapse APL harbored an average of eight non-silent somatic mutations per exome. We observed recurrent alterations of FLT3, WT1, NRAS and KRAS in the newly diagnosed APL, whereas mutations in other genes commonly mutated in myeloid leukemia were rarely detected. The molecular signature of APL relapse was characterized by emergence of frequent mutations in PML and RARA genes. Our sequencing data also demonstrates incidence of loss-of-function mutations in previously unidentified genes, ARID1B and ARID1A, both of which encode for key components of the SWI/SNF complex. We show that knockdown of ARID1B in APL cell line, NB4, results in large-scale activation of gene expression and reduced in vitro differentiation potential