The role of bone marrow transplantation in acute promyelocytic leukemia

Engineering stem cells for cancer immunotherapy

Engineering stem cells presents an attractive paradigm for cancer immunotherapy. Stem cells engineered to stably express various chimeric antigen receptors (CARs) or T-cell receptors (TCRs) against tumor-associated antigens are showing increasing promise in the treatment of solid tumors and hematologic malignancies. Stem cells engraft for long-term immune cell generation and serve as a sustained source of tumor-specific effector cells to maintain remissions. Furthermore, engineering stem cells provides 'off-the-shelf' cellular products, obviating the need for a personalized and patient-specific product that plagues current autologous cell therapies. Herein, we summarize recent progress of stem cell-engineered cancer therapies, and discuss the utility, impact, opportunities, and challenges of cellular engineering that may facilitate the translational and clinical research.

Role of hematopoietic cell transplantation in relapsed acute promyelocytic leukemia

The use of all trans-retinoic acid and arsenic trioxide combination as the induction regimen for acute promyelocytic leukemia (APL) has revolutionized the management and outcomes of this disease. Modern risk-adapted frontline therapy has provided excellent therapeutic results. However, significant numbers of APL patients relapse after frontline therapy, and the optimal management strategy for relapsed APL, specifically the role and type of hematopoietic cell transplantation (HCT) are still to be defined. Both autologous and allogeneic HCTs are associated with durable remission and prolonged survival when utilized in appropriate disease settings. Once remission has been achieved, consolidation with autologous HCT for APL patients with negative minimal residual disease (MRD) status, and with allogeneic HCT for APL patients with positive MRD status appear to offer the best long-term outcomes. In this article, we provide a comprehensive review of existing literature on the efficacy of HCT in treatment of relapse/refractory APL and we discuss the appropriate use of this modality.

Morphine Attenuated the Cytotoxicity Induced by Arsenic Trioxide in H9c2 Cardiomyocytes

Arsenic trioxide (ATO) is an efficient drug for the treatment of the patients with acute promyelocytic leukemia (APL). Inhibition of proliferation as well as apoptosis, attenuation of migration, and induction of differentiation in tumor cells are the main mechanisms through which ATO acts against APL. Despite advantages of ATO in treatment of some malignancies, certain harmful side effects, such as cardiotoxicity, have been reported. It has been well documented that morphine has antioxidant, anti-apoptotic, and cytoprotective properties and is able to attenuate cytotoxicity. Therefore, in this study, we aimed to investigate the protective effects of morphine against ATO toxicity in H9c2 myocytes using multi-parametric assay including thiazolyl blue tetrazolium bromide (MTT) assay, reactive oxygen species (ROS) generation, caspase 3 activity, nuclear factor kappa B (NF-κB) phosphorylation assay, and expression of apoptotic markers. Our results showed that morphine (1 μM) attenuated cytotoxicity induced by ATO in H9c2 cells. Results of this study suggest that morphine may have protective properties in management of cardiac toxicity in patients who receive ATO as an anti-cancer treatment.

Autologous transplant remains the preferred therapy for relapsed APL in CR2

Despite their favorable prognosis, 10-20% of acute promyelocytic leukemia (APL) patients relapse. Reinduction therapy is often followed by autologous hematopoietic cell transplantation (auto-HCT). Arsenic trioxide (ATO) has become part of standard reinduction and is often followed by auto-HCT. Data on patients in CR2 were collected from two large transplant registries (Center for International Blood and Marrow Transplant Research (CIBMTR) and European Group for Blood and Marrow Transplant (EBMT)) and two specialty referral centers. The outcome of patients in CR2 who received only ATO-based therapy as reinduction was retrospectively compared with those who got an auto-HCT, with or without ATO. Prognostic factors included age, disease risk, extramedullary disease and duration of CR1. Of 207 evaluable patients, the median age was 31.5 years, 15.3% had extramedullary disease and median WBC at diagnosis was 4.8 × 10(9)/L. Sixty-seven patients received ATO alone and 140 underwent auto-HCT. The groups were comparable for age, gender, extramedullary disease, risk group and duration of CR1. At 5 years, overall survival (OS) was 42% and 78% for the ATO-only and auto-HCT groups, respectively (P<0.001). In addition, OS was associated with longer duration of CR1 (P=0.002), but not with disease risk at diagnosis. These data suggest that auto-HCT for APL patients in CR2 results in better OS than ATO-based therapy alone.

Autologous is superior to allogeneic hematopoietic cell transplantation for acute promyelocytic leukemia in second complete remission

To identify favored choice of transplantation in patients with acute promyelocytic leukemia (APL) in second complete remission, we studied 294 patients with APL in second complete remission (CR2) receiving allogeneic (n = 232) or autologous (n = 62) hematopoietic cell transplantation (HCT) reported to the Center for International Blood and Marrow Transplantation Research (CIBMTR) from 1995 to 2006, including 155 with pre-HCT PML/RAR∝ status (49% of allogeneic and 66% of autologous). Patient characteristics and transplantation characteristics, including treatment-related mortality, overall survival (OS), and disease-free survival, were collected and analyzed for both univariate and multivariate outcomes. With median follow-up of 115 (allogeneic) and 72 months (autologous), 5-year disease-free survival (DFS) favored autologous with 63% (49% to 75%), compared with allogeneic at 50% (44% to 57%) (P = .10). OS was 75% (63% to 85%) versus 54% (48% to 61%) (P = .002), for autologous and allogeneic transplantation, respectively. Multivariate analysis showed significantly worse DFS after allogeneic HCT (hazard ratio [HR], 1.88; 95% confidence interval [CI], 1.16 to 3.06; P = .011) and age > 40 years (HR, 2.30; 95% CI, 1.44 to 3.67; P = .0005). OS was significantly worse after allogeneic HCT (HR, 2.66; 95% CI, 1.52 to 4.65; P= .0006); age > 40 (HR, 3.29; 95% CI, 1.95 to 5.54; P < .001), and first complete remission < 12 months (HR, 1.56; 95% CI, 1.07 to 2.26; P = .021). Positive pre-HCT PML-RAR∝ status in 17 of 114 allogeneic and 6 of 41 receiving autologous transplantation did not influence relapse, treatment failure, or survival in either group. The survival advantage for autografting was attributable to increased treatment-related mortality (TRM) in the allogeneic group of 30% compared to 2% in the autologous group, in addition to the added mortality associated with GVHD. We conclude that autologous HCT yields superior OS for APL in CR2. Long-term DFS in autologous recipients, even with minimal residual disease-positive grafts, remains an important subject for further study.

Hepatic veno-occlusive disease following stem cell transplantation: incidence, clinical course, and outcome

The occurrence of hepatic veno-occlusive disease (VOD) has been reported in up to 60% of patients following stem cell transplantation (SCT), with incidence varying widely between studies depending on the type of transplant, conditioning regimen, and criteria used to make the diagnosis. Severe VOD is characterized by high mortality and progression to multiorgan failure (MOF); however, there is no consensus on how to evaluate severity. This review and analysis of published reports attempts to clarify these issues by calculating the overall mean incidence of VOD and mortality from severe VOD, examining the effect of changes in SCT practice on the incidence of VOD over time, and discussing the methods used to evaluate severity. Across 135 studies performed between 1979 and October 2007, the overall mean incidence of VOD was 13.7% (95% confidence interval [CI]=13.3%-14.1%). The mean incidence of VOD was significantly lower between 1979-1994 than between 1994-2007 (11.5% [95% CI, 10.9%-12.1%] vs 14.6% [95% CI, 14.0%-15.2%]; P <.05). The mortality rate from severe VOD was 84.3% (95% CI, 79.6%-88.9%); most of these patients had MOF, which also was the most frequent cause of death. Thus, VOD is less common than early reports suggested, but the current incidence appears to be relatively stable despite recent advances in SCT, including the advent of reduced-intensity conditioning. The evolution of MOF in the setting of VOD after SCT can be considered a reliable indication of severity and a predictor of poor outcome.

Auto-SCT for AML in second remission: CALGB study 9620

We studied the feasibility and efficacy of a two-step approach to Auto-SCT for patients with AML in second remission. Step 1 consisted of consolidation chemotherapy using cytarabine 2000 mg/m(2) i.v. every 12 h for 4 days plus etoposide 40 mg/kg total dose by continuous i.v. infusion over the same 4 days. PBSC were collected after G-CSF stimulation during recovery from this chemotherapy. Step 2, auto-SCT, used a preparative regimen of oral BU 16 mg/kg over 4 days followed by etoposide 60 mg/kg i.v. Of the 50 patients entered on Step 1, two died from treatment complications, and seven failed to proceed to transplantation. A median CD34+ cell dose of 5.9 x 10(6)/kg was collected in a median of three collections. With a median follow-up of 8.2 years, 5-year disease-free survival (DFS) is 28%. The most important prognostic factor was cytogenetics, with acute promyelocytic leukemia (APL) patients having a 5-year DFS of 67% compared with 16% for others. We conclude that this two-step approach to autologous transplantation produces good CD34+ mobilization and that this approach has cured some patients. Results in patients with APL are especially promising.

Hematopoietic cell transplantation in acute promyelocytic leukemia: a comprehensive review

The past three decades have brought major therapeutic advances in the management of acute promyelocytic leukemia. The current state-of-the-art induction treatment with all-trans retinoic acid in combination with anthracycline-based chemotherapy results in long-lasting remissions and cure in up to 70% of newly diagnosed patients. Unfortunately, treatment failure still occurs in one-third of patients. When disease relapses, patients can achieve subsequent remissions with arsenic trioxide, all-trans retinoic acid with or without chemotherapy, or other therapies. Patients achieving molecular remissions after salvage therapy are generally considered candidates for high-dose chemotherapy and autologous hematopoietic cell transplantation as a postconsolidation strategy. On the other hand, patients with evidence of persistent hematologic or molecular disease after salvage therapy could be offered allogeneic hematopoietic transplantation if a suitable HLA-donor is identified and the patient's overall performance and clinical condition are permissible. We hereby provide a comprehensive review and analysis of published clinical trials that evaluate the role of hematopoietic cell transplantation across different stages of acute promyelocytic leukemia.

Reinduction of relapsed acute promyelocytic leukemia with ATRA and low dose antimetabolite-based chemotherapy

While the disease-free survival of acute promyelocytic leukemia (APML) now approaches 75%, some children continue to experience relapses, and questions remain as to the optimal management of these patients. We describe two young children who experienced combined relapses in the bone marrow and extramedullary locations following hematopoietic stem cell transplantation (HSCT). An induction regimen, consisting of all-trans retinoic acid (ATRA), methotrexate, and 6-mercaptopurine (6MP), successfully and safely achieved hematologic remission in one patient and molecular remission in the other. These cases demonstrate that there is a role for ATRA plus differentiating chemotherapy other than arsenic trioxide in the treatment of relapsed APML.

Hematopoietic stem cell transplantation for adults with acute promyelocytic leukemia in the ATRA era: a survey of the European Cooperative Group for Blood and Marrow Transplantation

We performed a survey of the European Cooperative Group for Blood and Marrow Transplantation to analyze the outcome of 625 acute promyelocytic leukemia (APL) patients transplanted with auto- or allogeneic-hematopoietic stem cell transplantation (autoHSCT, alloHSCT) after 1993, in first (CR1) or in second complete remission (CR2). Leukemia-free survival (LFS) at 5 years in CR1 was 69% for 149 patients autografted and 68% for 144 patients allografted, whereas in CR2, LFS was 51% in 195 autoHSCT and 59% in 137 alloHSCT recipients, respectively. In the group of autoHSCT for CR1 (n=149), higher relapse incidence (RI) was associated with shorter time from diagnosis to transplant (<7.6 months); transplant-related mortality (TRM) was increased in older patients (>47 years), whereas for CR2, longer time from diagnosis to transplant (>18 months) was associated with increased LFS and decreased RI. In the alloHSCT group for CR1 (n=144), age (<33 years) was associated with increased LFS and decreased TRM and for CR2 (n=137), the use of mobilized peripheral blood stem cells was associated with decreased TRM. Female recipient, a female donor to male recipient and transplants performed before 1997 were associated with decreased RI. In conclusion, HSCT still appears to have a role in APL, especially for patients in CR2.

Arsenic Trioxide Therapy in Relapsed or Refractory Japanese Patients with Acute Promyelocytic Leukemia: Updated Outcomes of the Phase II Study and Postremission Therapies

Recently, arsenic trioxide (ATO) has been proved to induce complete remission (CR) at a high rate in patients with acute promyelocytic leukemia (APL). We prospectively investigated the safety and efficacy of ATO therapy in patients with relapsed and refractory APL and examined the duration of CR and the postremission therapies. Initially, 0.15 mg/kg ATO was administered until bone marrow remission to a maximum of 60 days. After the patient achieved CR, 1 additional ATO course at the same dosage was administered for 25 days. Of 34 patients, 31 (91%) achieved CR. PML-RAR3 messenger RNA was not detected in the bone marrow of 18 (72%) of the 25 patients evaluated by reverse transcriptase-polymerase chain reaction analysis. At a median follow-up of 30 months, the estimated 2-year overall survival rate was 56%, and the estimated 2-year event-free survival rate was 17%. During the ATO therapy, QTc prolongation was observed in most cases. Fifteen patients developed ventricular tachycardia, and 1 of them showed torsades de pointes. Other adverse events were nausea, water retention, APL differentiation syndrome, skin eruption, liver dysfunction, and peripheral neuropathy, all of which were quite tolerable. ATO therapy was remarkably effective for relapsed APL; however, postremission therapies were necessary to maintain a durable remission.

Autologous and allogeneic stem-cell transplantation as salvage treatment of acute promyelocytic leukemia initially treated with all-trans-retinoic acid: a retrospective analysis of the European acute promyelocytic leukemia group

PURPOSE

To retrospectively determine the outcome of acute promyelocytic leukemia (APL) patients who underwent autologous or allogeneic stem-cell transplantation (SCT) during second complete remission.

PATIENTS AND METHODS

Of 122 relapsing patients included in two successive multicenter APL trials who achieved hematological second complete remission (generally after a salvage regimen of all-trans-retinoic acid [ATRA] combined with chemotherapy), 73 (60%) received allogeneic (n = 23) or autologous (n = 50) SCT.

RESULTS

Seven-year relapse-free survival (RFS), event-free survival (EFS), and overall survival (OS) in the autologous SCT group were 79.4%, 60.6%, and 59.8%, respectively, with a transplant-related mortality (TRM) of 6%. Of the 28 and two patients autografted with negative and positive, respectively, reverse transcriptase-polymerase chain reaction before auto SCT, three (11%) and one relapsed, respectively. In the allogeneic SCT group, 7-year RFS, EFS, and OS were 92.3%, 52.2%, and 51.8%, respectively, with 39% TRM. OS was significantly better in the autologous SCT group than in the allogeneic SCT group (P = .04), whereas RFS and EFS did not differ significantly (P = .19 and P = .11, respectively). In patients not receiving transplantation, 7-year RFS, EFS, and OS were 38%, 30.4%, and 39.5%, respectively.

CONCLUSION

These retrospective data suggest that autologous SCT is very effective in APL relapsing after treatment with ATRA if performed in molecular remission. Allogeneic SCT yields few relapses, but it is associated with high TRM when performed after salvage with very intensive chemotherapy. Salvage with arsenic trioxyde, which has lower toxicity, should further improve the outcome of relapsing APL, especially before allogeneic SCT.

Long-term remission of APL with a second allogeneic BMT after CNS relapse following HLA-identical allogeneic BMT

Second allogeneic bone marrow transplantation (BMT) for AML relapsing after an initial BMT has a poor prognosis, with a probability of a 2-y disease-free survival below 30 per cent, caused both by treatment-related mortality (TRM) and high relapse rate. While TRM is most likely due to heavy pretreatment, AML relapse after BMT may be due to resistant disease or to a poor graft-versus-leukaemia (GvL) effect of the transplant. The degree of GvL may depend on individual donor/recipient immunoreactivity. In most published cases of second allogeneic BMT, both transplants were performed from the same donor. Here, we describe a patient who was first transplanted for acute promyelocytic leukaemia (APL) (AML FAB M3v) from his HLA-identical brother and received intensive immunotherapy including donor lymphocytes and IL2. He remained free from GvHD >I degrees, but developed CNS relapse. After a second BMT from another HLA-identical brother, he spontaneously developed GvHD III degrees, and has now been disease free for nearly 3 years. In this patient, long-term remission of AML relapsing after BMT was achieved by combining remission induction using an individual chemotherapy protocol with a second BMT from an alternative matched related donor and transient GvHD III degrees, which probably conferred a GVL effect.

Allogeneic stem cell transplantation for advanced acute promyelocytic leukemia: results in patients treated in second molecular remission or with molecularly persistent disease

In all, 17 consecutive patients in hematological complete remission (HCR) of acute promyelocytic leukemia (APL) received allogeneic stem cell transplantation (SCT) from an HLA-identical sibling and were monitored by reverse transcriptase polymerase chain reaction of PML/RARalpha prior and after transplant. Median age was 31 years (range 3-50 years). At 10 years, the actuarial probabilities of nonrelapse mortality, relapse and disease-free survival were 32% (95% CI: 8-56%), 33% (95% CI: 6-60%) and 46% (95% CI: 22-70%). Six patients tested PCR +ve (1st HCR n=2; 2nd HCR n=3; 3rd HCR n=1) and 11 PCR -ve (2nd HCR n=11) pre-SCT. Of the six patients PCR +ve, two showed early persistence of PCR positivity and converted to sustained PCR negativity after CSA withdrawal (one died of secondary tumor in molecular remission and one is alive in relapse), while four converted to PCR -ve rapidly (one died of the underlying disease and three are in molecular remission). Of the 11 patients PCR -ve pre-SCT, six died (four of transplant-related mortality, one of relapse and one after heart transplantation) and five are alive, four in molecular remission and one is in relapse. Allogeneic SCT seems a valid option for advanced APL, particularly for the poor prognostic group of patients with pre-SCT molecularly persistent disease.

Arsenic trioxide (trisenox) therapy for acute promyelocytic leukemia in the setting of hematopoietic stem cell transplantation

The relapse-free survival of patients with acute promyelocytic leukemia (APL) has significantly increased during the last decade. The introduction of all-trans retinoic acid (ATRA) doubled the survival of patients with this disease. However, despite ATRA and anthracycline-based chemotherapy, 12%-30% of patients will still relapse. Arsenic trioxide (ATO) has demonstrated efficacy and safety in patients with first and subsequent relapsed or refractory APL, regardless of the disease-free interval. Treatment of relapsed and refractory patients with this novel therapy produces complete remission in 87% of patients and molecular remission in 83%. Studies have documented the efficacy of autologous and allogeneic transplantation as salvage therapy in relapsed and refractory APL. The introduction of ATO into the treatment regimen for APL has stimulated discussion on its role in the transplantation setting. Investigators recently met to discuss the issue and make recommendations regarding ATO therapy in patients who are in their second or subsequent complete remission and are candidates for transplantation. This article describes the pivotal studies of this novel agent, discusses risk factor stratification for relapse in patients with APL, and proposes protocols for treatment incorporating ATO therapy. In addition, it describes scientific issues in ongoing and proposed clinical trials of ATO therapy for this disease.

Acute promyelocytic leukaemia in children

Acute promyelocytic leukaemia (APL), designated M3, is a particularly interesting subtype of acute myeloid leukaemia (AML) that has unique molecular and clinical characteristics. It is characterized by an arrest of myeloid differentiation at the promyelocyte stage with abnormal proliferation of these cells. Recent paediatric and adult trials which included all-trans retinoic acid (ATRA) have shown that APL has significantly better survival rates than other subtypes of AML. While there is extensive literature on APL in adults, articles dedicated to describing solely paediatric patients are limited. This chapter focuses on the incidence, diagnosis, clinical characteristics, treatment, and survival rates of children with APL.

Choice of chemotherapy in induction, consolidation and maintenance in acute promyelocytic leukaemia

Cure of acute promyelocytic leukaemia (APL) is now a reality for most patients through the use of combined all-trans retinoic acid (ATRA) and chemotherapy. The simultaneous administration of ATRA and anthracycline-based chemotherapy is currently considered the most appropriate induction therapy. However, no consensus has been reached on the consolidation strategy. Therapeutic efficacy apparently did not differ according to the number of cycles and types of drug combined with anthracyclines. Encouraging results have been reported recently using less-intensive chemotherapy with anthracyclines alone, leading to a significant reduction in treatment-related toxicity during the consolidation phase and a high degree of compliance. Some ongoing risk-adapted protocols are now exploring the potential synergistic effect of ATRA and chemotherapy given simultaneously in consolidation. Preliminary data suggest that higher molecular remission rates post-consolidation and improved outcome may be obtained through this strategy. Persistence or recurrence of molecular disease at the end of consolidation is strongly associated with impending relapse and poor prognosis, indicating the need for further aggressive therapy. As for maintenance therapy, once demonstrated, the advantage of using ATRA with or without low-dose methotrexate and 6-mercaptopurine has encouraged most groups to incorporate such treatment into their protocols for APL.

Acute myeloid leukemia

In this chapter, Drs. Keating and Willman review recent advances in our understanding of the pathophysiology of acute myeloid leukemia (AML) and allied conditions, including the advanced myelodysplastic syndromes (MDS), while Drs. Goldstone, Avivi, Giles, and Kantarjian focus on therapeutic data with an emphasis on current patient care and future research studies. In Section I, Dr. Armand Keating reviews the role of the hematopoietic microenvironment in the initiation and progression of leukemia. He also discusses recent data on the stromal, or nonhematopoietic, marrow mesenchymal cell population and its possible role in AML. In Section II, Drs. Anthony Goldstone and Irit Avivi review the current role of stem cell transplantation as therapy for AML and MDS. They focus on data generated on recent Medical Research Council studies and promising investigation approaches. In Section III, Dr. Cheryl Willman reviews the current role of molecular genetics and gene expression analysis as tools to assist in AML disease classification systems, modeling of gene expression profiles associated with response or resistance to various interventions, and identifying novel therapeutic targets. In Section IV, Drs. Hagop Kantarjian and Francis Giles review some promising agents and strategies under investigation in the therapy of AML and MDS with an emphasis on novel delivery systems for cytotoxic therapy and on targeted biologic agents.

Autologous stem cell transplantation for acute myeloid leukemia

Autologous bone marrow transplant (ABMT) and stem cell transplantation (ASCT) are important treatment modalities for acute myeloid leukemia (AML). The role of ASCT in first remission patients remains controversial. Phase II and phase III studies demonstrate that patients with favorable-risk cytogenetics benefit from ASCT, with reduction in relapse and improvement in leukemia-free survival (LFS). Patients with poor-risk cytogenetics do not appear to benefit significantly from ASCT and should preferentially be treated with allogeneic transplant. The role of ASCT for patients with intermediate risk disease is uncertain. It appears that ASCT in first remission will improve disease-free survival compared to standard chemotherapy. Sufficient patients who relapse after chemotherapy treatment can be salvaged with ASCT in second remission such that the beneficial effect on overall survival is blunted. ASCT produces equivalent results to ABMT but with reduced morbidity. The collection of stem cells during recovery from intensive dose consolidation therapy appears to be an attractive strategy that can increase the percentage of patients who are able to receive their intended transplant. Consolidation therapy prior to stem cell collection and transplant has been shown to decrease the relapse rate and improve outcomes, but the optimal nature of this consolidation therapy is unknown. For patients with AML in second remission, ABMT/ASCT offers a substantial salvage rate, and is particularly effective for patients with acute promyelocytic leukemia.

Acute promyelocytic leukemia: a case-based review

Retinoid therapy for acute promyelocytic leukemia (APL) is one of the major achievements of leukemia research in the last 15 years. Use of all trans retinoic acid (ATRA) has changed the prognosis of APL from a fatal leukemia to a highly curable disease. This case-based review examines the available clinical and scientific data to form evidence-based decisions in the management of APL. The main aim of this review is to highlight recent progress made in the management of APL and address the role of maintenance therapy, prognostic factors for relapse and treatment of relapsed disease.

Management of acute promyelocytic leukemia

Acute promyelocytic leukemia (APL) has become the most potentially curable subtype of acute myeloid leukemia (AML) in adults. With current treatment strategies that incorporate all-trans retinoic acid (ATRA), long-term disease-free survival and potential cure rates of 70% to 80% can be expected. Such progress reflects what can be accomplished with insights into the molecular pathogenesis of leukemia, identification of a molecular target, and rapid accrual to a series of clinical trials. The leukemic promyelocytes from patients with APL are uniquely susceptible to a variety of novel agents in addition to ATRA, including arsenic trioxide, and in preliminary studies, gemtuzumab ozogamicin, the immunoconjugate comprised of an anti-CD33 monoclonal antibody linked to the potent cytotoxic agent calicheamicin. Incorporation of such agents into the treatment of patients with high-risk disease may be an important future direction to pursue.

New advances in the treatment of acute promyelocytic leukemia

OBJECTIVE

Describe the treatment options of newly diagnosed and relapsed APL.

INDUCTION

The fusion PML/RAR gene provided the rationale for using all-trans retinoic acid (ATRA) as differentiation therapy. The standard approach is antracycline + ATRA and no ARA-C.

CONSOLIDATION

Anthracycline based chemotherapy, no high dose ARA-C and perhaps no ARA-C. Maintenance seems to be important. Cure with ATRA + chemotherapy increased to 75% from 35% with chemotherapy alone.

POOR PROGNOSIS FACTORS

WBC >10,000, age >55, platelets <40,000 and CD 56 expression. Achieving and maintaining a molecular remission (MCR) i.e. RT-PCR (-) for PML/RAR alpha expression, is the best predictor for cure. Conversion to PCR (+) will eventually result in relapse. PCR monitoring in the first 2 years and intervention during molecular relapse would be safer than treatment in clinical relapse. Molecular relapses have been treated successfully by ATRA plus BMT. Arsenic trioxide (ATO) or gentuzumab (mylotarg) are also being studied.

RELAPSE (INDUCTION)

Patients after ATRA in first CR are less likely to respond to ATRA reinduction regardless of the time off ATRA and rarely achieve a molecular remission. Single-agent ATO induced in 52 relapsed patients CR of 87% (75% MCR) with low toxicity and no treatment related deaths (U.S. pivotal trial), confirmed in a NCI trial. Induction of relapsing patients with single agent ATO is preferable than ATRA + chemotherapy because the high molecular remission and lower toxicity.

RELAPSE (POST REMISSION)

No standard approach and the role of chemotherapy is unknown. ATO alone: in the pivotal trial, 9/21 patients had long remissions without other therapy. BMT: Not indicated in 1st MCR. In young patients auto BMT with PCR (-) harvests could be done in subsequent CR. Allo BMT has a higher death rate without overall better results. In the pivotal trial 12 patients were transplanted in CR after ATO alone (9 allo BMT) and 11 still without disease. Possibly allo BMT is safer after a less toxic ATO induction.

OTHER

ATO plus ATRA +/- AntiCD33 conjugated with toxin (gentuzumab) or 131I; Synthetic retinoid (Am80); histone deacetylase inhibitors; oral tetra-arsenic tetra-sulfide and various combinations.

Arsenic trioxide therapy for relapsed or refractory Japanese patients with acute promyelocytic leukemia: need for careful electrocardiogram monitoring

Recent studies have shown that arsenic trioxide (As(2)O(3)) can induce complete remission in patients with acute promyelocytic leukemia (APL). We tested the efficacy and safety of As(2)O(3) for the treatment of patients with APL who had relapsed from or become refractory to all-trans retinoic acid (ATRA) and conventional chemotherapy in a prospective study. As(2)O(3) at a dose of 0.15 mg/kg was administered until the date of bone marrow remission to a maximum of 60 days. In patients who achieved complete remission (CR), one additional course of As(2)O(3) was administered using the same dose for 25 days. Of 14 patients, 11 (78%) achieved CR. Six of 10 patients who achieved CR showed disappearance of PML-RARalpha transcript by RT-PCR assay. The duration of As(2)O(3)-induced CR ranged from 4 to 22 months (median, 8 months) at a median follow-up of 17 months. Adverse events included 13 electrocardiogram abnormalities (13 QTc prolongation, eight ventricular premature contraction, four nonsustained ventricular tachycardia and two paroxysmal supraventricular tachycardia), seven nausea and vomiting, four pruritus, three peripheral neuropathy, three fluid retention and one APL differentiation syndrome. Four patients received antiarrhythmic agents. Hyperleukocytosis developed in five patients and in three cytotoxic drugs were necessary. Other adverse events were relatively mild. As(2)O(3) treatment is effective and relatively safe in relapsed or refectory patients with APL. Cardiac toxicities in patients with QTc prolongation should be carefully monitored.

Autologous stem cell transplantation for adult acute leukemia

Autologous stem cell transplantation using marrow or peripheral blood is routinely used to consolidate patients with acute myelocytic leukemia in complete remission. The situation is less clear for adult acute lymphocytic leukemia in which results achieved with all strategies are disappointing. In acute myelocytic leukemia, autografts should be done in patients with good and standard risk factors. Patients with high-risk acute myelocytic leukemia defined by poor cytogenetics or failure to achieve remission with the first induction course, should proceed to allogeneic stem cell transplantation with the best available human leukocyte antigen-identical donor (family or unrelated), and the nature of the conditioning regimen (myelo-ablative or non-myelo-ablative) should be decided in relation to age, and the patient's clinical condition. Results of autografting in acute myelocytic leukemia rely strongly on the quality of the graft. Higher doses of infused stem cells translate into lower relapse rates. Marrow purging with cyclophosphamide derivatives also diminishes the relapse incidence. Autologous stem cell transplantations using peripheral blood are presently preferred to marrow as the source of stem cells, but an aggressive prior in vivo purge (high-dose consolidation course(s) before cytaphereses) is then mandatory. In good-risk acute myelocytic leukemia, autografting is superior to high-dose ARA-C; in standard-risk acute myelocytic leukemia, both are supposedly equivalent. There is no prospective randomized study testing the two approaches in the good-standard-risk population. We presently test the combination of marrow and blood both purged by mafosfamide. In adult acute lymphocytic leukemia, good-risk patients get the best benefit from autografting over conventional chemotherapy. Maintenance chemotherapy after transplant is likely to bring benefit. Research in progress aims at facilitating access of the largest number of patients to autografting and at introducing posttransplant immunomodulation maneuvers such as tumor vaccination.

Acute promyelocytic leukemia: evolving therapeutic strategies

Acute promyelocytic leukemia (APL) is now the most curable subtype of acute myeloid leukemia in adults. All-trans retinoic acid (ATRA), which induces differentiation of the leukemic cells into mature granulocytes, represents the important advance. The incorporation of ATRA in induction results in a high complete remission rate, leads to rapid resolution of the characteristic life-threatening coagulopathy, and, most importantly, decreases the relapse rate compared with treatment with chemotherapy alone. However, ATRA is associated with unique toxicities not observed with conventional cytotoxic chemotherapy. A number of clinical trials have been performed to define the optimal role of ATRA in the treatment of patients. The therapeutic strategies have rapidly evolved as a result of both single institution and large cooperative group trials. Arsenic trioxide and stem cell transplantation are effective treatments for patients with APL who relapse after or are refractory to ATRA-based therapy. As experience with ATRA and arsenic trioxide in patients with APL accumulates, a number of important questions arise that need to be addressed.