Oral arsenic trioxide for relapsed acute promyelocytic leukemia in pediatric patients

Chemotherapy-free approaches to newly-diagnosed acute promyelocytic leukemia: is oral-arsenic trioxide/all-trans retinoic acid/ascorbic acid the answer?

INTRODUCTION

Acute promyelocytic leukemia (APL) is a distinct form of acute myeloid leukemia characterized by the presence of t(15;17)(q24;21) and the PML:RARA gene fusion. Frontline use of intravenous arsenic trioxide (i.v.-ATO) and all-trans retinoic acid (ATRA) has vastly improved cure rates in APL. Researchers in Hong Kong invented the oral formulation of ATO (oral-ATO) and have confirmed a bioavailability comparable to i.v.-ATO. A plethora of studies have confirmed the safety and efficacy of oral-ATO-based regimens in the frontline and relapsed setting.

AREAS COVERED

Aspects on the development of oral-ATO-based regimens for APL in the frontline and relapsed setting are discussed. The short-term and long-term safety and efficacy of oral-ATO-based regimens are discussed. The frontline use of oral-ATO in combination with ATRA and ascorbic acid (AAA) induction in a 'chemotherapy-free' is highlighted.

EXPERT OPINION

Current and ongoing data on the use of oral-ATO-based regimens in APL support the use of oral-ATO as an alternative to i.v.-ATO allowing a more convenient and economical approach to the management of APL.

An overview of arsenic trioxide-involved combined treatment algorithms for leukemia: basic concepts and clinical implications

Arsenic trioxide is a first-line treatment drug for acute promyelocytic leukemia, which is also effective for other kinds of leukemia. Its side effects, however, limit its clinical application, especially for patients with complex leukemia symptoms. Combination therapy can effectively alleviate these problems. This review summarizes the research progress on the combination of arsenic trioxide with anticancer drugs, vitamin and vitamin analogs, plant products, and other kinds of drugs in the treatment of leukemia. Additionally, the new progress in arsenic trioxide-induced cardiotoxicity was summarized. This review aims to provide new insights for the rational clinical application of arsenic trioxide.

Acute promyelocytic leukaemia: population-based study of epidemiology and outcome with ATRA and oral-ATO from 1991 to 2021

BACKGROUND

The epidemiology and treatment of acute promyelocytic leukaemia (APL) are changing. We have incorporated oral arsenic trioxide (oral-ATO) into induction/maintenance.

METHODS

Newly-diagnosed APL from 1991 to 2021 divided into three 10-year periods were studied to define its epidemiology and how oral-ATO impacted on its outcome. Primary endpoints included APL incidence, early deaths (ED, first 30 days), and overall survival (OS). Secondary endpoints included post-30-day OS, relapse-free survival (RFS), and incidence of second cancers.

RESULTS

APL occurred in 374 males and 387 females at a median age of 44 (1-97) years. Annual incidences increased progressively, averaging 0.32 per 100,000 people. All-trans retinoic acid (ATRA)-based and oral-ATO-based regimens were used in 469 and 282 patients. There were 144 EDs, occurring almost exclusively in ATRA-based inductions (N = 139), being more with males, age > 50 years, leucocyte > 10 × 10⁹/L, diagnosis during 1991-2009 and fewer with oral-ATO-based regimens. After a median of 75 (interquartile range: 14-161) months, 5-year and 10-year OS were 68.1% and 63.3%, inferior with males, age > 50 years, leucocyte > 10 × 10⁹/L, high-risk Sanz score and superior with oral-ATO-based regimens. Factoring out EDs, 5-year and 10-year post-30-day OS were 84.0% and 78.1%, inferior with males and superior with oral-ATO-based regimens. In 607 CR1 patients, the 5-year RFS was 83.8%, superior with diagnosis in 2010-2021 and oral-ATO-based regimens. Second cancers developed in 21 patients, unrelated to oral-ATO-based regimens.

CONCLUSIONS

There was an increasing incidence of APL, and all survivals were superior with the use of oral-ATO-based regimens. This study formed part of the Acute Promyelocytic Leukaemia Asian Consortium Project (ClinicalTrials.gov identifier: NCT04251754).

Excellent Early Outcomes of Combined Chemotherapy With Arsenic Trioxide for Stage 4/M Neuroblastoma in Children: A Multicenter Nonrandomized Controlled Trial

This nonrandomized, multicenter cohort, open-label clinical trial evaluated the efficacy and safety of combined chemotherapy with arsenic trioxide (ATO) in children with stage 4/M neuroblastoma (NB). We enrolled patients who were newly diagnosed with NB and assessed as stage 4/M and received either traditional chemotherapy or ATO combined with chemotherapy according to their own wishes. Twenty-two patients were enrolled in the trial group (ATO combined with chemotherapy), and 13 patients were enrolled in the control group (traditional chemotherapy). Objective response rate (ORR) at 4 weeks after completing induction chemotherapy was defined as the main outcome, and adverse events were monitored and graded in the meantime. Data cutoff date was December 31, 2019. Finally, we found that patients who received ATO combined with chemotherapy had a significantly higher response rate than those who were treated with traditional chemotherapy (ORR: 86.36% vs. 46.16%, p=0.020). Reversible cardiotoxicity was just observed in three patients who were treated with ATO, and no other differential adverse events were observed between the two groups. ATO combined with chemotherapy can significantly improve end-induction response in high-risk NB, and our novel regimen is well tolerated in pediatric patients. These results highlight the superiority of chemotherapy with ATO, which creates new opportunity for prolonging survival. In addition, this treatment protocol minimizes therapeutic costs compared with anti-GD2 therapy, MIBG, and proton therapy and can decrease the burden to families and society. However, we also need to evaluate more cases to consolidate our conclusion.

A practical strategy to subcutaneous administered in-situ gelling co-delivery system of arsenic and retinoic acid for the treatment of acute promyelocytic leukemia

Arsenic trioxide (ATO) combined with all trans retinoic acid (ATRA) is the first choice for the treatment of low and medium risk acute promyelocytic leukemia (APL). Clinical studies reported that the combination of ATO and ATRA could achieve a significant curative effect. However, the retinoic acid syndrome, serious drug resistance and the short half-life in vivo which lead to frequent and large dose administration limit the application of ATRA. In addition, the preparations of arsenic are conventional injections and tablets in clinic, which has poor patients' compliance caused by frequent long-term administration and serious side effects. In order to overcome the above limitations, a phospholipid phase separation gel (PPSG) loaded with ATO and ATRA was developed. ATO+ATRA-PPSG (AAP), as a biodegradable sustained-release delivery system, was the first achievement of co-delivery of hydrophilic ATO and lipophilic ATRA with high drug loading which is the main problem in the application of nano preparation. The prepared PPSG displayed high safety and biocompatibility. The drug in PPSG was released slowly and continuously in vivo and in vitro for up to 10 d, which could reduce the side effects caused by the fluctuation of blood drug concentration and solve the problem of the long treatment cycle and frequent administration. In vivo pharmacokinetics depicted that PPSG could improve the bioavailability, decrease the peak concentration, and prolong the t1/2 of ATO and ATRA. Particularly, AAP significantly inhibited the tumor volume, extended the survival period of tumor-bearing mice, and promoted the differentiation of APL cells into normal cells. Therefore, ATO+ATRA-PPSG not only could co-load hydrophilic ATO and lipophilic ATRA according to the clinical dosage, but also possessed the sustained-release and long-acting treatment effect which was expected to reduce administration time and ameliorate compliance of patients. Thus, it had great potential for clinical transformation and application.

Characteristics and predictors of early hospital deaths in newly diagnosed APL: a 13-year population-wide study

Despite therapeutic advances, early death (ED) remains a major factor curtailing survival of acute promyelocytic leukemia (APL). Studies examining factors that cause early death (ED; within 30 days of admission) and the correlation of survival with the timing of administration of all-trans retinoic acid (ATRA) and hemostatic parameters are scarce. We performed a cohort analysis of nonselect patients with newly diagnosed APL who presented to the health care system in Hong Kong, where oral arsenic trioxide was used. From 1 January 2007 to 30 April 2020, 358 patients (median age, 47 [1-97] years) with newly diagnosed APL were identified. ED occurred in 56 patients (16%): 11 (3%) died in the first 2 days after admission (intracranial hemorrhage [ICH], n = 6; APL-differentiation syndrome [APL-DS], n = 4; infection, n = 1); 22 (6%) died within 3 to 7 days (ICH, n = 12; APL-DS, n = 8; infections, n = 2), and 23 (6%) died within 8 to 30 days (ICH, n = 7; APL-DS, n = 11; infection, n = 5). Factors significantly associated with ED by multivariate analysis included male sex (P = .01); presenting leukocyte count ≥10 × 109/L (P = .03); fibrinogen <1.5 g/L (P = .02); and ATRA administration >24 hours after hospital admission (P < .001). After a median follow-up of 47 (0-166) months, the 5- and 10-year overall survival (OS) was 68.6% and 61.2%, respectively. Excluding EDs, the 5- and 10-year post-30-day OS improved to 81.3% and 72.5%. Early administration of ATRA (<24 hours) and vigorous correction of hemostatic abnormalities, including hypofibrinogenemia, are key to reducing ED.

Development of arsenic trioxide sustained-release pellets for reducing toxicity and improving compliance

Arsenic trioxide (ATO) is first-line drug for acute promyelocytic leukemia. Clinically, the continuously slow intravenous infusion is adopted to maintain effective blood concentration and reduce toxic effects, but it causes poor patient' compliance for a considerable infusion period. To overcome these disadvantages, we developed an oral ATO sustained-release preparation which was constructed via the ATO core pellets prepared by extrusion spheronization and followed by a coating membrane by fluid-bed technology. The prepared coated pellets displayed a round surface and uniform particle size. All in vitro release profiles of ATO pellets in different pH media and rotation speeds had no statistical difference. Importantly, the coated pellets can release completely in 12 h without obvious burst release. There was no distinct change in appearance and release behaviors in stability experiments. In vivo pharmacokinetics was studied by one-time intragastric administration of rats. Compared with free drug, the AUC_0-∞ of the ATO coated pellets was 2.3-fold higher, indicating the oral bioavailability was significantly increased. C_max decreased by about a half and T_max extended about 15 h. In particularly, the ATO level at 96 h only decreased about 20% of C_max , suggesting that the ATO sustained-release preparation could not only decrease the peak concentration, but also maintain a relatively constant blood concentration for a long period. Further, the in vivo absorption could be well predicted by in vitro release experiments. Therefore, the ATO sustained-release preparation formulated by the mature preparation technology, possessing satisfactory stability and improving bioavailability, had great application potentials for industrialization.

Oral arsenic trioxide, all-trans retinoic acid, and ascorbic acid maintenance after first complete remission in acute promyelocytic leukemia: Long-term results and unique prognostic indicators

BACKGROUND

The role of arsenic trioxide (As₂ O₃ ) in the maintenance of first complete remission (CR1) in acute promyelocytic leukemia (APL) is unclear.

METHODS

A total of 129 consecutive adult patients with APL of all risk categories who achieved CR1 with conventional induction (all-trans retinoic acid [ATRA]/daunorubicin) and consolidation (daunorubicin/cytarabine [induction daunorubicin and consolidation omitted for age ≥70 years]) underwent maintenance comprising ATRA (45 mg/m² /day), oral As₂ O₃ (10 mg/day), and ascorbic acid (1 g/day) (AAA) for 2 weeks every 2 months for 2 years.

RESULTS

Over a 17-year period from August 1, 2002, to July 31, 2019, 63 men and 66 women (median age, 46 years [range, 18-82 years]) received AAA maintenance, which was already completed in 117 patients. At a median follow-up of 100 months (range, 8-215 months), 17 patients (13%) developed first relapse (R1) (hematologic, n = 14; molecular, n = 3) after a median of 19 months (range, 7-96 months) from CR1. Two R1 patients had concomitant central nervous system (CNS) involvement. All patients achieved CR2 with oral As₂ O₃ -based salvage. Five patients had a subsequent relapse and died. Eight patients died of unrelated causes while still in CR1. The 5-year and 10-year rates of relapse-free survival (RFS) were 89% and 85%, respectively. The 5-year and 10-year rates of overall survival (OS) were 94% and 87%, respectively. Multivariate analysis showed that inferior RFS was associated with FLT3-ITD (P = .005) and CNS involvement on presentation (P = .004), and inferior OS was associated with therapy-related APL (P = .03), FLT3-ITD (P = .03), and relapse (P = .03). The safety profile was favorable, with no grade 3/4 organ toxicities.

CONCLUSION

CR1 maintenance with AAA is safe and results in favorable long-term survival in patients with APL.

Combinatorial Low Dose Arsenic Trioxide and Cisplatin Exacerbates Autophagy via AMPK/STAT3 Signaling on Targeting Head and Neck Cancer Initiating Cells

Head and neck squamous cell carcinoma (HNSCC) is a highly lethal disease with high-level of epidemic both in the world and Taiwan. Previous studies support that head and neck cancer-initiating cells (HN-CICs), a subpopulation of cancer cells with enhanced stemness properties, contribute to therapy resistance and tumor recurrence. Arsenic trioxide (As₂O₃; ATO) has shown to be an effective anti-cancer drug targeting acute promyelocytic leukemia (APL). Combinatorial treatment with high dose of ATO and cisplatin (CDDP) exert synergistic apoptotic effects in cancer cell lines of various solid tumors, however, it may cause of significant side effect to the patients. Nevertheless, none has reported the anti-cancerous effect of ATO/CDDP targeting HN-CICs. In this study, we aim to evaluate the low dose combination of ATO with conventional chemo-drugs CDDP treatment on targeting HN-CICs. We first analyzed the inhibitory tumorigenicity of co-treatment with ATO and chemo-drugs on HN-CICs which are enriched from HNSCC cells. We observed that ATO/CDDP therapeutic regimen successfully synergized the cell death on HN-CICs with a Combination Index (CI) <1 by Chou-Talalay's analysis in vitro. Interestingly, the ATO/CDDP regimen also induced exaggerated autophagy on HN-CICs. Additionally, this drug combination strategy also empowered both preventive and therapeutic effect by in vivo xenograft assays. Finally, we provide the underlying molecular mechanisms of ATO-based therapeutic regimen on HN-CICs. Together, low dose of combinatorial ATO/CDDP regimen induced cell death as well as exacerbated autophagy via AMPK-STAT3 mediated pathway in HN-CICs.

Oral arsenic trioxide incorporation into frontline treatment with all-trans retinoic acid and chemotherapy in newly diagnosed acute promyelocytic leukemia: A 5-year prospective study

BACKGROUND

Strategies using oral arsenic trioxide (As₂ O₃ ) are efficacious in relapsed acute promyelocytic leukemia (APL), but they have not been examined in newly diagnosed cases.

METHODS

Sixty-two consecutive patients (24 men and 38 women) with a median age of 52 years (range, 22-85 years), 36% of whom had high-risk features, underwent induction with all-trans retinoic acid at 45 mg/m² /d, oral As₂ O₃ at 10 mg/d, and ascorbic acid at 1 g/d (the all-trans retinoic acid-arsenic trioxide-ascorbic acid [AAA] regimen) for 6 weeks (with patients younger than 70 years additionally receiving daunorubicin at 50 mg/m² /d × 3); they then underwent consolidation with 2 monthly cycles of daunorubicin (50 mg/m² /d × 2) and cytarabine (100 mg/m² /d × 5) and received AAA maintenance (2 weeks every 8 weeks) for 2 years. A contemporaneous cohort of 37 newly diagnosed patients (15 men and 22 women) with a median age of 51 years (range, 23-78 years), not consenting to oral As₂ O₃ induction but receiving similar induction, consolidation, and AAA maintenance, served as a comparator group; 46% of these patients had high-risk features.

RESULTS

The oral As₂ O₃ induction cohort showed a complete remission (CR) rate of 100%. After a median of 37 months (range, 13-82 months), there were no relapses, so conventional risks (age, leukocyte and platelet counts, and Fms-like tyrosine kinase 3 [FLT3] mutations) were not relevant. The leukemia-free survival (LFS) and overall survival (OS) rates were 100% at 3 years and 94.1% at 5 years. The non-As₂ O₃ induction cohort showed a CR rate of 100%. After a median of 52 months (range, 14-77 months), there were 3 relapses (8%). Comparable patients in the oral As₂ O₃ induction and non-As₂ O₃ induction cohorts showed similar OS, but LFS was significantly superior in the oral As₂ O₃ induction cohort.

CONCLUSIONS

The incorporation of oral As₂ O₃ into induction for newly diagnosed APL was safe and decreased relapses.

Pre-application of arsenic trioxide may potentiate cytotoxic effects of vinorelbine/docetaxel on neuroblastoma SK-N-SH cells

BACKGROUND

Arsenic trioxide is effective in the treatment of acute promyelocytic leukemia and is currently in use in clinical trials for the treatment of solid tumor types. Given that arsenic trioxide is able to arrest neuroblastoma cell cycle in the G2/M phase, the present study is, to the best of our knowledge, the first to investigate whether the combination of arsenic trioxide with mitosis-phase-specific antineoplastic agents (vinorelbine or docetaxel) or non-mitosis-phase-specific antineoplastic agents (etoposide or cisplatin) exert synergistic effects in cytotoxicity on the human SK-N-SH neuroblastoma cell line.

METHODS

Neuroblastoma cells were either incubated with one of the four drugs individually, or preincubated with arsenic trioxide and then followed by another drug when cell cycle was arrested at the G2/M phase with the highest proportion.

RESULTS

The results of the present study revealed that arsenic trioxide potentiated the apoptotic rate of neuroblastoma cells induced by chemotherapeutic drugs. The present study further demonstrated that preincubation with arsenic trioxide followed by a mitosis-phase-specific antineoplastic agent result in a higher cytotoxicity effect compared with a non mitosis-phase-specific antineoplastic agent. Along with the enhanced cytotoxicity in combination group, the cell cycle distribution demonstrated a decreased proportion of G2/M phase in the combination group.

CONCLUSION

The in vitro study revealed that the pre-application of arsenic trioxide followed by mitosis-phase-specific antineoplastic agents potentiate the cytotoxic effects on neuroblastoma cells, therefore arsenic trioxide may be a promising therapeutic option for treating neuroblastoma.

Long-term outcome of relapsed acute promyelocytic leukemia treated with oral arsenic trioxide-based reinduction and maintenance regimens: A 15-year prospective study

BACKGROUND

For patients who have acute promyelocytic leukemia (APL) in second complete remission (CR2), optimal postremission strategies remain undefined.

METHODS

The role of an oral arsenic trioxide (As₂ O₃ )-based regimen in the management of patients who had APL in CR2 was examined.

RESULTS

Seventy-three patients with APL in first relapse (R1) were studied. Oral As₂ O₃ -based reinduction resulted uniformly in CR2, irrespective of previous As₂ O₃ exposure. All patients received oral As₂ O₃ -based maintenance in CR2. At a median follow-up of 94 months (range, 9-205 months), 43 patients (58.9%) were still in CR2, and 49 (67.1%) had finished the planned 2-year CR2 maintenance with all-trans retinoic acid, oral As₂ O₃ , and ascorbic acid. Reinduction and maintenance treatments were well tolerated. Grade 1 and 2 headache occurred in 20 patients (27.4%). Hepatotoxicity, all in the form of transaminitis, occurred in 35 patients (47.9%; grade 1 and 2, n = 26; grade 3 and 4, n = 9). Three patients had self-limiting QTc prolongation. The 10-year leukemia-free survival rate was 56.8%. Thirty patients developed R2. Oral As₂ O₃ -based reinduction led to CR3 in 27 patients (90%). Post-CR3 strategies included autologous hematopoietic stem cell transplantation and oral As₂ O₃ maintenance. At a post-CR3 follow-up of 30 months (range, 3-166 months), 11 patients were still in CR3. The 5-year and 10-year overall survival rates in the R1 cohort were 79.5% and 67.3%, respectively. Prior receipt of oral As₂ O₃ maintenance in CR1 was the only risk factor for inferior leukemia-free survival. Central nervous system involvement occurred in 15 patients, including 5 who remained alive. Relapse during oral As₂ O₃ therapy was the only significant risk factor for central nervous system involvement.

CONCLUSIONS

For patients with relapsed APL, As₂ O₃ remained effective despite repeated As₂ O₃ exposures. Oral As₂ O₃ maintenance was an effective postremission strategy for CR2. Cancer 2018;124:2316-26. © 2018 American Cancer Society.

Retinoic acid and arsenic trioxide in the treatment of acute promyelocytic leukemia: current perspectives

Acute promyelocytic leukemia (APL) is a distinct subtype of acute myeloid leukemia (AML) with a unique morphological appearance, associated coagulopathy and canonical balanced translocation of genetic material between chromosomes 15 and 17. APL was first described as a distinct subtype of AML in 1957 by Dr Leif Hillestad who recognized the pattern of an acute leukemia associated with fibrinolysis, hypofibrinogenemia and catastrophic hemorrhage. In the intervening years, the characteristic morphology of APL has been described fully with both classical hypergranular and variant microgranular forms. Both are characterized by a balanced translocation between the long arms of chromosomes 15 and 17, [t(15;17)(q24;q21)], giving rise to a unique fusion gene PML-RARA and an abnormal chimeric transcription factor (PML-RARA), which disrupts normal myeloid differentiation programs. The success of current treatments for APL is in marked contrast to the vast majority of patients with non-promyelocytic AML. The overall prognosis in non-promyelocytic AML is poor, and although there has been an improvement in overall survival in patients aged <60 years, only 30%-40% of younger patients are still alive 5 years after diagnosis. APL therapy has diverged from standard AML therapy through the empirical discovery of two agents that directly target the molecular basis of the disease. The evolution of treatment over the last 4 decades to include all-trans retinoic acid and arsenic trioxide, with chemotherapy limited to patients with high-risk disease, has led to complete remission in 90%-100% of patients in trials and rates of overall survival between 86% and 97%.

Low dose of arsenic trioxide inhibits multidrug resistant-related P-glycoprotein expression in human neuroblastoma cell line

This study investigated arsenic trioxide (As2O3), cisplatin (DDP) and etoposide (Vp16) on the anticancer effects and P-glycoprotein (P-gp) expression in neuroblastoma (NB) SK-N-SH cells. The potential influence of As2O3, DDP and Vp16 currently included in NB routine treatment protocols on cytotoxicity in SK-N-SH cells was measured by flow cytometry and drug half-maximal inhibitory concentration (IC50) was established. Moreover, chemotherapeutic agent-mediated changes of cellular expression levels of resistant-related P-gp, was monitored using western blotting. The data showed that As2O3, DDP and Vp16 significantly inhibited the growth and survival of the SK-N-SH cells at different concentration. Notably, the levels of apoptosis were upregulated in SK-N-SH cells with an acceleration of the exposure time and the concentration of As2O3, DDP and Vp16. As2O3, DDP and Vp16 were observed with their IC50 values on SK-N-SH cells being 3 µM, 8 and 100 µg/ml, respectively. Flow cytometry analysis showed that As2O3 at low concentrations in SK-N-SH cells led to enhanced accumulation of cell populations in G2/M phase with increasing the exposure time, and increased levels of apoptosis. In contrast, we observed that SK-N-SH cell populations arrested in S phase by DDP and Vp16. In vitro examination revealed that following pretreatment of SK-N-SH cells with As2O3, the expression of P-gp was not increased. The expression of P-gp downregulation were noted following the group treated by As2O3 at 2 and 3 µM. Exposed to As2O3 at 3 µM for 72 h, SK-N-SH cells exhibited lower expression of P-gp than 2 µM As2O3 for 72 h. In contrast, the expression of P-gp was upregulated by DDP and VP16. In summary, SK-N-SH cells were responsive to chemotherapeutic agent-induced apoptosis in a dose-dependent and time-dependent manner. In particular, ours findings showed that low dose of As2O3 markedly reduced the P-gp expression and increased apoptotic cell death in human NB cell line.

Same sibling marrow following cord allogeneic transplantation as therapy for second relapse acute promyelocytic leukemia in a pediatric patient

Optimal therapy for relapsed APL in pediatric patients is controversial. Allogeneic HSCT is an alternative, with event-free survival of 70-75%. We report a pediatric patient with APL who relapsed 28 months after CBT from her sibling and then was treated with BMT from the same donor. Bone marrow was selected for higher cell dose, donor availability, and partial donor chimerism. Persistent molecular remission was achieved, currently at 65 months after BMT. This case suggests the potential role of GVL activity in APL and illustrates the use of different cell sources from the same donor in allogeneic transplantation for pediatric patients.

Acute Promyelocytic Leukemia (APL): Comparison Between Children and Adults

The outcome of adults and children with Acute Promyelocytic Leukemia (APL) has dramatically changed since the introduction of all trans retinoic acid (ATRA) therapy. Based on the results of several multicenter trials, the current recommendations for the treatment of patients with APL include ATRA and anthracycline-based chemotherapy for the remission induction and consolidation, and ATRA combined with low-dose chemotherapy for maintenance. This has improved the prognosis of APL by increasing the complete remission (CR) rate, actually > 90%, decreasing the induction deaths and by reducing the relapse rate, leading to cure rates nowadays exceeding 80% considering both adults and children.1-9 More recently the combination of ATRA and arsenic trioxide (ATO) as induction and consolidation therapy has been shown to be at least not inferior and possibly superior to ATRA plus chemotherapy in adult patients with APL conventionally defined as non-high risk (Sanz score).10 Childhood APL has customarily been treated on adult protocols. Data from several trials have shown that the overall outcome in pediatric APL appears similar to that reported for the adult population; however, some clinical and therapeutic aspects differ in the two cohorts which require some important considerations and treatment adjustments.

Treatment of an acute promyelocytic leukemia relapse using arsenic trioxide and all-trans-retinoic in a 6-year-old child

In adult therapy, arsenic trioxide (ATO) and all-trans-retinoic acid (ATRA) are recognized as active treatment of relapsed acute promyelocytic leukemia (APL). The efficacy of this combination in pediatric APL has not yet been well established. We report the case of a 6-year-old girl with relapsed APL, with a PML-RARα mutation, treated with a combination of ATO and ATRA. Over a period of 5 months, she received in total, 75 doses of intravenous ATO and 40 doses of oral ATRA. Currently, 22 months after relapse, she is still in complete remission. Here, we describe treatment of a relapsed APL in a child with limited treatment of ATO and ATRA and review the literature.

Role of arsenic trioxide in acute promyelocytic leukemia

Acute promyelocytic leukemia (APL) is a unique subtype of acute myeloid leukemia that is characterized by distinct clinical, morphological, cytogenetic, and molecular abnormalities. It is associated with a striking risk of early hemorrhagic death due to disseminated intravascular coagulation and hyperfibrinolysis. The prognosis of APL has improved dramatically following the introduction of all-trans retinoic acid (ATRA) and its combination with anthracycline-based chemotherapy during induction and consolidation. Patients with high-risk APL, defined by a white cell count >10 × 10(9)/L at diagnosis, also appear to benefit from the addition of intermediate- or high-dose cytarabine during consolidation. Arsenic trioxide (ATO) has proved to be even more effective than ATRA as a single agent, and is now routinely used for the treatment of the 20%-30% of patients who manifest disease relapse after initial treatment with ATRA and chemotherapy. ATO has a toxicity profile that differs considerably from that of both ATRA and cytotoxic chemotherapy, and accordingly presents its own specific challenges during treatment. Optimizing a strategy for the incorporation of ATO into initial therapy is currently the focus of several cooperative group trials, with an emphasis on minimizing or even eradicating the use of chemotherapy. ATRA plus ATO without chemotherapy appears to be adequate during induction and consolidation for patients with standard-risk APL, but triple therapy that includes limited anthracycline or gemtuzumab ozogamicin (GO) during induction is required for high-risk APL. Uncertainty still exists regarding the minimum amount of chemotherapy and number of consolidation cycles necessary, the optimal scheduling of ATO, and the potential utility of oral ATO administration. Although prolonged oral maintenance therapy is usually included in most current APL treatment protocols, its value remains controversial, and the superior anti-leukemic efficacy of ATO-based therapy may facilitate its elimination in the future.

How I treat children and adolescents with acute promyelocytic leukaemia

Acute promyelocytic leukaemia (APL) is a rare subtype of acute myeloid leukaemia. The outcome of paediatric APL has improved substantially over the past 20 years; cure rates above 80% are expected when all-trans retinoic acid (ATRA) is given with anthracycline-based regimens. The presenting features of paediatric APL may include severe bleeding and thrombotic complications, which contribute to the high early death rate. The incidence of leucocytosis and the microgranular subtype is greater in paediatric than adult APL, and children experience greater ATRA-related toxicity. It is crucial to begin ATRA therapy and intensive platelet and fibrinogen replacement on first suspicion of APL. Recent risk-adapted therapeutic trials have shown that patients at greater risk of relapse benefit from the introduction of high-dose cytarabine during consolidation. Combination therapy with ATRA and arsenic trioxide provides very effective frontline treatment and may reduce the need for subsequent anthracycline therapy.