Presenting White Blood Cell Count and Kinetics of Molecular Remission Predict Prognosis in Acute Promyelocytic Leukemia Treated With All-Trans Retinoic Acid: Result of the Randomized MRC Trial

Diagnosis and management of acute promyelocytic leukemia: Brazilian consensus guidelines 2024 on behalf of the Brazilian Association of Hematology, Hemotherapy and Cellular Therapy

Improvements in clinical assessment have occurred since the last published recommendations on the diagnosis and treatment of acute promyelocytic leukemia in 2013. Here, a committee of specialists of the Brazilian Association of Hematology, Hemotherapy and Cellular Therapy presents a comprehensive review on the current knowledge, focusing on the advances in diagnosis, risk assessment, and frontline and salvage therapy. The concept of urgent diagnosis is explored as well as the management of critical situations such as coagulopathy and differentiation syndrome. Recent adjustments in risk stratification based on white blood cell counts only are presented together with the incorporation of chemo-free regimens for non-high-risk patients. Special conditions such as acute promyelocytic leukemia in children, the elderly and pregnant women are discussed. Finally, acute promyelocytic leukemia is presented as a highly curable disease because of the real possibility of targeted therapy towards differentiation, and, paradoxically, as a serious and urgent condition that deserves prompt recognition and management to avoid early mortality.

Complications during Induction Chemotherapy in Acute Promyelocytic Leukemia: An Institutional Experience

Stalin Chowdary BalaIntroduction  Acute promyelocytic leukemia (APL) has transformed from a highly fatal disease to a highly curable one. Induction deaths continue to represent one of the major impediments in modern therapy of APL. Sepsis, hemorrhage, and differentiation syndrome are the major complications during induction therapy in APL. The present study reports the incidence and prognostic factors of major complications during induction chemotherapy in patients with newly diagnosed APL. Materials and Methods  The present study was a single institutional, observational, retrospective study. All cases of APL diagnosed by morphology and confirmed by RT PCR (PML RARα) were included in this study. Data were analyzed using Statistical Package for the Social Sciences (SPSS) version 25. Results  A total of 73 patients were analyzed. The median age at presentation was 30 years (range, 3-60 years) with a female to male ratio of 1.02:1. The most common symptom at presentation was fever (80%), followed by fatigue (56%) and gum bleeding (37%). The majority of the patients at presentation were high risk (42.4%), followed by intermediate risk (38.4%) and low risk (19.2%). Fifty-seven (78%) patients achieved complete hematological remission and 16 (22%) succumbed during induction chemotherapy. Infection was the most common cause of induction death (50%), followed by hemorrhage (37.5%) and differentiation syndrome (12.5%). On univariate analysis of prognostic factors, bcr3 variant, grade 3/4 bleeding during induction, and low levels of albumin at presentation were significant for induction mortality ( p  = 0.034, 0.041, and 0.008 respectively). On multivariate analysis, only serum albumin < 3.5 g/dL was an independent predictor for induction mortality ( p  = 0.043). Conclusion  The majority of patients were high risk at presentation. Sepsis was the most common complication during induction and also the leading cause of induction death. Identifying induction complications at the earliest and providing aggressive supportive measures can further improve outcomes in APL.

Therapy-Related Acute Promyelocytic Leukemia: A Case Report and a Review of Literature

Acute promyelocytic leukemia (APL) is a subgroup of acute myeloid leukemia (AML), and while not a common form of cancer, it does make up a modest portion of acute leukemia. The genetic hallmark of APL is the t(15;17)(q24.1;q21.2) promyelocytic leukemia/retinoic acid receptor alpha (PML/RARA) protein. We present the case of a patient who had undergone prior therapy for stage IIIC squamous cell carcinoma of the anorectal region with 5-fluorouracil, mitomycin C, and radiation and developed therapy-related acute promyelocytic leukemia about 18 months later. We also review the clinical features and management of APL while also highlighting that therapy-related APL, although uncommon, can develop from chemoradiation. The specific diagnosis of therapy-related APL is its own distinct diagnosis, but its treatment remains the same as primary APL.

Long-term retrospective study of retinoic acid combined with arsenic and chemotherapy for acute promyelocytic leukemia

Chemotherapy, all-trans retinoic acid (ATRA), and arsenic are effective options for acute promyelocytic leukemia (APL). We conducted a 20-year retrospective analysis of newly diagnosed (ND) APL patients treated with arsenic, ATRA and mitoxantrone. After achieving complete remission (CR), patients received 3-5 cycles of chemotherapy followed by AS4S4 maintenance for 3 years. Eighty-eight ND APL patients were treated with either oral AS4S4 (n = 42) or arsenic trioxide (ATO) (n = 46). The 8-year overall survival (OS) rate was 100% in the AS4S4 group and 90% in the ATO group. The disease-free survival (DFS) rates were 100% and 87.1% (p = 0.027), respectively. Patients in the ATO group had more side effects. A subsequent cohort of 33 ND APL patients received triple therapy with oral AS4S4, ATRA, and chemotherapy. The 13-year OS and DFS rates were 100% and 90.9%. Our long-term analyses show that APL patients with oral AS4S4 had better outcomes compared to ATO, with no need for hospitalization.

Analysis of risk factors for early death in patients with acute promyelocytic leukaemia treated with arsenic trioxide

To date, no specific studies have evaluated early death (ED) in patients with acute promyelocytic leukaemia (APL) homogeneously treated with arsenic trioxide induction therapy and investigated according to the white blood cell (WBC) count at onset. Such patients were retrospectively analysed in this study, including 314 patients with a WBC count ≤ 10 × 10⁹/L (standard-risk (SR) group) and 144 with a WBC count > 10 × 10⁹/L (high-risk (HR) group). The baseline clinical characteristics and risk factors for ED were compared between the two groups. The incidence of fibrinogen < 1.0 g/L and elevated serum uric acid, aspartate aminotransferase and creatinine levels were higher in the HR group than in the SR group (P = 0.001; P < 0.001; P < 0.001; P = 0.044, respectively). The ED rate was significantly higher in the HR group than in the SR group (29.17% vs. 10.83%, P < 0.001). The main cause of ED was bleeding, followed by infection and differentiation syndrome (DS) in the HR group, while it was bleeding, followed by DS and infection in the SR group. Male sex, age > 50 years old, and fibrinogen < 1.0 g/L were independent risk factors for ED in the SR group. Increased serum creatinine levels, decreased albumin levels, and fibrinogen < 1.0 g/L were independent risk factors for ED in the HR group. Overall, the incidence of ED was higher in the HR group, and the baseline clinical characteristics, causes, times, and predictors of ED in the HR group differed from those in the SR group.

Value of measurable residual disease monitoring in patients with acute promyelocytic leukemia in the era of frontline 'chemotherapy-free' therapy

Acute promyelocytic leukemia (APL) is characterized by the chromosomal translocation t(15;17) and the resulting gene PML-RARA, used for measurable residual disease (MRD) monitoring. Despite highly effective therapy for APL, MRD monitoring practices are not fully established. We aimed to assess the value of MRD monitoring by RT-qPCR in patients with APL treated with ATRA and arsenic trioxide +/- GO. We reviewed 223 patients with APL treated with this regimen. RT-qPCR for PML-RARA was measured every 3 months, and at 12, 18, and 24 months after therapy. Seven patients relapsed. Time to relapse was 7.9-12.4 months in 6 patients, and one patient relapsed after 79.5 months. These data show that MRD monitoring may be important for the detection of relapse in patients treated with this regimen within one year after completing therapy, however, since late molecular relapse is rare, our data suggest a low value of MRD monitoring beyond that first year.

A phase 2 study of ATRA, arsenic trioxide, and gemtuzumab ozogamicin in patients with high-risk APL (SWOG 0535)

High-risk acute promyelocytic leukemia (APL) remains a therapeutic challenge, with higher associated rates of early mortality and relapse than standard-risk APL. All-trans retinoic acid (ATRA) plus arsenic trioxide (ATO) is a well-established treatment for patients with standard-risk APL, but it is not well defined for those with high-risk APL. In a prior study of patients with high-risk APL, the addition of gemtuzumab ozogamicin (GO) to ATO plus ATRA suggested benefit. The SWOG Cancer Research Network conducted a phase 2 study to confirm the efficacy and safety of the combination of ATRA plus ATO plus GO in treating high-risk APL patients. The primary end points were 3-year event-free survival (EFS) and early (6-week) death rates associated with this combination. Seventy patients were treated. With a median follow-up of 3.4 years, the 3-year EFS and overall survival estimates were 78% (95% confidence interval [CI], 67%-86%) and 86% (95% CI, 75%-92%), respectively. Overall, 86% of patients achieved complete response. The 6-week mortality rate was 11%. The most common treatment-emergent toxicities during the induction phase included febrile neutropenia, aspartate aminotransferase/alanine aminotransferase elevation, hyperglycemia, hypoxia, headache, and prolonged QT interval corrected for heart rate. Retinoic acid syndrome occurred in 9% of patients. Approximately 37% of patients did not complete all planned courses of postremission therapy. The combination of ATRA plus ATO plus GO in high-risk APL patients was effective and generally well tolerated, suggesting an opportunity to offer a chemotherapy-free induction platform for patients with this disease. This trial was registered at www.clinicaltrials.gov as #NCT00551460.

Incidence of Differentiation Syndrome Associated with Treatment Regimens in Acute Myeloid Leukemia: A Systematic Review of the Literature

Differentiation syndrome (DS) is a potentially fatal adverse drug reaction caused by the so-called differentiating agents such as all-trans retinoic acid (ATRA) and arsenic trioxide (ATO), used for remission induction in the treatment of the M3 subtype of acute myeloid leukemia (AML), acute promyelocytic leukemia (APL). However, recent DS reports in trials of isocitrate dehydrogenase (IDH)-inhibitor drugs in patients with IDH-mutated AML have raised concerns. Given the limited knowledge of the incidence of DS with differentiating agents, we conducted a systematic literature review of clinical trials with reports of DS to provide a comprehensive overview of the medications associated with DS. In particular, we focused on the incidence of DS reported among the IDH-inhibitors, compared to existing ATRA and ATO therapies. We identified 44 published articles, encompassing 39 clinical trials, including 6949 patients. Overall, the cumulative incidence of DS across all treatment regimens was 17.7%. Incidence of DS was notably lower in trials with IDH-inhibitors (10.4%) compared to other regimens, including ATRA and/or ATO (15.4-20.6%). Compared to other therapies, the median time to onset was four times longer with IDH-inhibitors (48 vs. 11 days). Treating oncologists should be mindful of this potentially fatal adverse drug reaction, as we expect the current trials represent an underestimation of the actual incidence.

Clinical significance of increased PML-RARa transcripts after induction therapy for acute promyelocytic leukaemia

Objective: To analyze the clinical and biological significance of the acute promyelocytic leukemia (APL) whose PML-RARa transcripts increased after induction therapy.Methods: We analyzed 9 cases of APL whose PML-RARa transcripts increased after induction treatment and compare them with APL whose PML-RARa transcripts decreased.Results: The only factor affecting increased PML-RARa transcripts was the induction protocol. The cases of increased PML-RARa transcripts received induction treatment mainly based on ATRA and ATO. The evaluation of bone marrow aspirate cytology showed that the cell percentage from myelocyte to segmented neutrophil of the patients with increased PML-RARa transcripts was significantly higher than that of the patients with decreased PML-RARa transcripts. In the follow-up, MRD in 9 cases was consistently negative.Conclusions: Our studies showed the increased PML-RARa transcripts after induction treatment had different clinical significance from the decreased PML-RARa transcripts.

Impact of CD56 Continuously Recognizable as Prognostic Value of Acute Promyelocytic Leukemia: Results of Multivariate Analyses in the Japan Adult Leukemia Study Group (JALSG)-APL204 Study and a Review of the Literature

BACKGROUND

After long-term analysis of the JALSG-APL204 study we recently reported that maintenance therapy with tamibarotene was more effective than all-trans retinoic acid (ATRA) by reducing relapse in APL patients. Here, the clinical significance of other important prognostic factors was evaluated with multivariate analyses.

PATIENTS AND METHODS

Newly diagnosed acute promyelocytic leukemia (APL) patients were registered with the study. Induction was composed of ATRA and chemotherapy. Patients who achieved molecular remission after consolidation were randomly assigned to maintenance with tamibarotene or ATRA.

RESULTS

Of the 344 eligible patients, 319 (93%) achieved complete remission (CR). After completing consolidation, 269 patients underwent maintenance random assignment-135 to ATRA, and 134 to tamibarotene. By multivariate analysis, overexpression of CD56 in blast was an independent unfavorable prognostic factor for relapse-free survival (RFS) (p = 0.006) together with more than 10.0 × 10⁹/L WBC counts (p = 0.001) and the ATRA arm in maintenance (p = 0.028). Of all phenotypes, CD56 was related most clearly to an unfavorable prognosis. The CR rate, mortality rate during induction and overall survival of CD56⁺ APL were not significantly different compared with CD56^- APL. CD56 is continuously an independent unfavorable prognostic factor for RFS in APL patients treated with ATRA and chemotherapy followed by ATRA or tamibarotene maintenance therapy.

Hematopoietic stem cell transplantation for pediatric acute promyelocytic leukemia in Japan

BACKGROUND

The number of hematopoietic stem cell transplantation (HSCT) procedures performed for pediatric acute promyelocytic leukemia (APL) has decreased in the all-trans retinoic acid (ATRA) era. Although HSCT is still widely adopted as part of salvage therapy for relapsed patients, there is no general consensus about the optimal transplant type (autologous [auto-HSCT] or allogeneic HSCT [allo-HSCT]).

PROCEDURES

We retrospectively reviewed the clinical data of 95 childhood APL patients who underwent their first HSCT between 1990 and 2014. Of the 95 patients, 40 (42%), 41 (43%), and 3 (3%) underwent HSCT procedures after achieving their first complete remission (CR1), CR2, and CR3, respectively, and 11 (12%) underwent HSCT while in a non-CR state.

RESULTS

The non-CR group exhibited significantly worse five-year overall survival (5yOS) and disease-free survival (5yDFS) (5yOS: 46%; 5yDFS: 46%) than the CR1 (5yOS: 80%; 5yDFS: 78%) and CR2 + CR3 groups (5yOS: 81%; 5yDFS: 76%) (P = 0.013 and P < 0.01, respectively). Of the patients treated in CR2, no significant differences in 5yOS or the five-year cumulative incidence of relapse (5yRI) were detected between the auto-HSCT and allo-HSCT groups (5yOS: 85%, vs 78%, P = 0.648; 5yRI: 9%, vs 11%, P = 0.828). Among the patients who underwent allo-HSCT in CR2, those with matched sibling donors displayed a significantly higher 5yRI (33%) than those with other types of donors (0%, P = 0.015).

CONCLUSIONS

Even after relapsing, childhood APL can be cured with HSCT if CR is achieved. These findings demonstrate that achieving CR followed by HSCT is the preferred strategy for treating children with relapsed or refractory APL.

Acute Promyelocytic Leukemia: A Constellation of Molecular Events around a Single PML-RARA Fusion Gene

Although acute promyelocytic leukemia (APL) is one of the most characterized forms of acute myeloid leukemia (AML), the molecular mechanisms involved in the development and progression of this disease are still a matter of study. APL is defined by the PML-RARA rearrangement as a consequence of the translocation t(15;17)(q24;q21). However, this abnormality alone is not able to trigger the whole leukemic phenotype and secondary cooperating events might contribute to APL pathogenesis. Additional somatic mutations are known to occur recurrently in several genes, such as FLT3, WT1, NRAS and KRAS, whereas mutations in other common AML genes are rarely detected, resulting in a different molecular profile compared to other AML subtypes. How this mutational spectrum, including point mutations in the PML-RARA fusion gene, could contribute to the 10%–15% of relapsed or resistant APL patients is still unknown. Moreover, due to the uncertain impact of additional mutations on prognosis, the identification of the APL-specific genetic lesion is still the only method recommended in the routine evaluation/screening at diagnosis and for minimal residual disease (MRD) assessment. However, the gene expression profile of genes, such as ID1, BAALC, ERG, and KMT2E, once combined with the molecular events, might improve future prognostic models, allowing us to predict clinical outcomes and to categorize APL patients in different risk subsets, as recently reported. In this review, we will focus on the molecular characterization of APL patients at diagnosis, relapse and resistance, in both children and adults. We will also describe different standardized molecular approaches to study MRD, including those recently developed. Finally, we will discuss how novel molecular findings can improve the management of this disease.

Application of Mie theory for enhanced size determination of microparticles using optical particle counters

The approach to particle sizing with optical particle counters is often simple interpolation of calibration data. A method is presented that uses the results of Mie-theory-based simulations to describe the signal between calibration points, thus reducing the number of necessary calibration points or increasing the sizing accuracy significantly. Through the use of Mie theory, particles with a refractive index differing from the calibration particles can be measured without an individual calibration. The method can be used with custom research setups or commercially available optical particle counters with various detector designs. If needed, the method can be applied to particle counters for which only the light wavelength used is known. The method is tested using a commercially available optical particle counter with a polystyrene microsphere calibration, measuring polystyrene microspheres as well as THP-1 cells, Chinese hamster ovary cells, and yeast cells. Without material specific calibration, simple interpolation results in about half the actual particle sizes for these biological samples, whereas the presented method yields accurate results.

Optimal Measurable Residual Disease Testing for Acute Myeloid Leukemia

Increasing evidence supports the prognostic significance of measurable residual disease (MRD) in acute myeloid leukemia (AML). Dynamic MRD assessment for patients with AML complements baseline patient risk assessment factors in determining patient prognosis. MRD status may also be helpful in informing therapeutic decisions. The European Leukemia Net MRD working party recently issued consensus recommendations for the use of MRD in AML. The Food and Drug Administration also issued advice for using MRD in trials of hematologic malignancies. This article discusses MRD testing, highlights the challenges in adopting MRD testing in clinical practice, and provides insights into the future of the field.

Outcome for pediatric acute promyelocytic leukemia patients at Children's Oncology Group sites on the Leukemia Intergroup Study CALGB 9710 (Alliance)

BACKGROUND

Acute promyelocytic leukemia (APL) is a unique leukemia subtype requiring specialized treatment including all-trans retinoic acid (ATRA). A prior report demonstrated worse outcome among young children <5 years old compared with older children.

METHODS

We evaluated outcomes for pediatric patients (<18 years old; N = 83) with APL treated on North American intergroup study CALGB 9710 at Children's Oncology Group sites. Induction and consolidation included ATRA, cytarabine, and anthracyclines. Patients ≥15 years old were randomized to addition of arsenic trioxide (ATO) consolidation. All patients were randomized to ATRA maintenance with versus without oral chemotherapy.

RESULTS

The estimated 5-year overall survival (OS) rate was 82%, and the event-free survival (EFS) rate was 54%. Seven patients (8.4%) died during induction due to coagulopathy. Maintenance randomization demonstrated that addition of oral chemotherapy to ATRA significantly reduced relapse rate, but difference in EFS did not reach statistical significance (P = 0.12; 5-year rates [95% CI]: 41% [17%-64%] ATRA only vs 72% [56%-88%] ATRA plus chemotherapy). There was no difference (P = 0.93) in EFS for age <5 years versus 5-12.99 years versus 13-17.99 years (5-year rates: 56%, 47%, and 45%, respectively). Among adolescents 15-17.99 years old in the ATO randomization, there was a significantly lower relapse risk at 5 years for those receiving ATO (0% ATO vs 44% no ATO; P = 0.02).

CONCLUSION

Our data demonstrate that intensified ATRA, cytarabine, and anthracycline chemotherapy is effective for pediatric APL including very young patients, but early deaths and relapses remain barriers to cure. Further improvements are likely with incorporation of ATO into pediatric APL regimens.

Intravenous arsenic trioxide and all-trans retinoic acid as front-line therapy for low-risk acute promyelocytic leukemia

INTRODUCTION

The outcome of acute promyelocytic leukemia (APL) has drastically improved following the identification of the PML-RARA oncogene as a key player in the pathogenesis of APL, and the subsequent introduction of all-trans retinoic acid (ATRA) as a therapeutic agent. Areas covered: Randomized trials have recently demonstrated the efficacy of arsenic trioxide (ATO) in combination with ATRA for the front-line treatment of standard and medium risk APL patients. This chemotherapy-free combination is associated with a decreased cumulative rate of relapse, prolonged overall survival, and reduced early death rate. Expert commentary: The most challenging issue in the management of APL remains the significant rate of early deaths in high-risk patients. The ongoing studies will clarify the possible role of ATO in this setting in combination with ATRA and other agents. The aim of this review is to report data of efficacy and safety of intravenous ATO in newly diagnosed patients and discuss on its potential role as a new standard of care for APL patients.

Is it time to routinely incorporate MRD into practice?

Interest in detecting minimal/measurable residual disease (MRD) in acute myeloid leukemia (AML) has been increasing, but numerous issues need to be addressed if MRD assessment is to be routinely incorporated into practice. Assays, their reliability, standardization, and availability all must be considered, and a strategy developed to eradicate residual leukemia. This paper reviews some issues surrounding the routine incorporation of MRD assessment into practice.

Tamibarotene maintenance improved relapse-free survival of acute promyelocytic leukemia: a final result of prospective, randomized, JALSG-APL204 study

Between April 2004 and December 2010, we conducted a prospective randomized controlled study comparing tamibarotene with all-trans retinoic acid (ATRA) in the maintenance therapy of newly diagnosed acute promyelocytic leukemia (APL), and here report the final results of this study with a median follow-up of 7.3 years. Of 344 eligible patients who had received ATRA and chemotherapy, 319 (93%) achieved complete remission (CR). After completion of three courses of consolidation chemotherapy, 269 patients in molecular remission underwent maintenance randomization, 135 to ATRA (45 mg/m² daily), and 134 to tamibarotene (6 mg/m² daily) for 14 days every 3 months for 2 years. The primary endpoint was relapse-free survival (RFS). The 7-year RFS was 84% in the ATRA arm and 93% in the tamibarotene arm (p = 0.027, HR = 0.44, 95% CI, 0.21 to 0.93). The difference was prominent in high-risk patients with initial leukocytes ≥ 10.0 × 10⁹/L (62% vs. 89%; p = 0.034). Tamibarotene was significantly superior to ATRA by decreasing relapse in high-risk patients. Overall survival after randomization did not differ (96% vs. 97%; p = 0.520). Secondary hematopoietic disorders developed in nine patients, secondary malignancies in 11, and grade 3 or more late cardiac comorbidities in three. These late complications did not differ between the two arms.

Molecular remission as a therapeutic objective in acute promyelocytic leukemia

Acute promyelocytic leukemia (APL) is a subtype of acute leukemia characterized by a unique t(15;17) translocation generating the PML/RARA fusion gene and hybrid oncoprotein. Besides its critical role in leukemogenesis, this genetic aberration serves as a disease-specific biomarker for rapid diagnosis and monitoring of minimal residual disease (MRD). Moreover, PML/RARA is specifically targeted by All-trans retinoic acid (ATRA) and arsenic trioxide (ATO), two agents that synergistically act to induce degradation of the oncoprotein. Large clinical studies including two randomized trials conducted in newly diagnosed APL patients have shown that the ATRA-ATO combination is superior to conventional ATRA and chemotherapy both in terms of efficacy and safety. Preliminary studies using oral formulations of arsenic and ATRA suggest that oral arsenic is as effective and manageable as intravenous ATO. Following early retrospective studies indicating the prognostic relevance of PML/RARA monitoring, several prospective studies were conducted in large cohorts of APL patients enrolled in clinical trials with the aim of better assessing the prognostic value of longitudinal PCR testing. The results consistently showed that molecular remission (defined as negativization of the PCR test for PML/RARA) correlates with a significantly decreased risk of relapse, whereas persistence of PCR positivity for PML/RARA after consolidation or conversion from negative to positive during follow-up is strongly associated with hematologic relapse. Based on these data, various groups started using pre-emptive salvage therapy for patients who persisted PCR-positive after frontline consolidation or converted from negative to positive PCR during follow-up. Finally, several expert panels have recommended that molecular remission should be considered a therapeutic objective in APL, and molecular response has been adopted as a study endpoint in modern clinical trials.

Acute promyelocytic leukemia with a cryptic insertion of RARA into PML on chromosome 15 due to uniparental isodisomy: A case report

Acute promyelocytic leukemia is a myeloid disorder that is characterized by the specific t(15;17) variant in ~98% of cases. The typical hypergranular and microgranular or hypogranular types exist, and are frequently associated with disseminated intravascular coagulopathy. Rare cases of promyelocytic leukemia-retinoic acid receptor α (PML-RARA) fusion without the reciprocal RARA-PML have been reported in cytogenetically normal samples. Conversely, fluorescence in situ hybridization (FISH) analysis has revealed a cryptic insertion of the RARA gene into the PML gene on chromosome 15. The current study reports a unique case with a normal karyotype and molecular evidence of the PML-RARA short isoform 3-fusion transcript, with FISH analysis revealing two fusion signals on the two copies of chromosome 15, but absence of the reciprocal on the two copies of chromosome 17. This finding raised the hypothesis of chromosome 15 uniparental isodysomy as consequence of normal chromosome 15 loss and duplication of the rearranged chromosome, as supported by polymorphic loci molecular analysis. The clinical, cytogenetic and molecular characterization of this case are presented and discussed in the present study.

Long-term outcome of acute promyelocytic leukemia treated with all-trans-retinoic acid, arsenic trioxide, and gemtuzumab

The combination of all-trans-retinoic acid (ATRA) plus arsenic trioxide (ATO) has been shown to be superior to ATRA plus chemotherapy in the treatment of standard-risk patients with newly diagnosed acute promyelocytic leukemia (APL). A recent study demonstrated the efficacy of this regimen with added gemtuzumab ozogamicin (GO) in high-risk patients. We examined the long-term outcome of patients with newly diagnosed APL treated at our institution on 3 consecutive prospective clinical trials, using the combination of ATRA and ATO, with or without GO. For induction, all patients received ATRA (45 mg/m² daily) and ATO (0.15 mg/kg daily) with a dose of GO (9 mg/m² on day 1) added to high-risk patients (white blood cell count, >10 × 10⁹/L), as well as low-risk patients who experienced leukocytosis during induction. Once in complete remission, patients received 4 cycles of ATRA plus ATO consolidation. One hundred eighty-seven patients, including 54 with high-risk and 133 with low-risk disease, have been treated. The complete remission rate was 96% (52 of 54 in high-risk and 127 of 133 in low-risk patients). Induction mortality was 4%, with only 7 relapses. Among low-risk patients, 60 patients (45%) required either GO or idarubicin for leukocytosis. Median duration of follow-up was 47.6 months. The 5-year event-free, disease-free, and overall survival rates are 85%, 96%, and 88%, respectively. Late hematological relapses beyond 1 year occurred in 3 patients. Fourteen deaths occurred beyond 1 year; 12 were related to other causes. This study confirms the durability of responses with this regimen.

Autologous hematopoietic cell transplantation for acute promyelocytic leukemia in second complete remission: outcomes before and after the introduction of arsenic trioxide

We conducted a retrospective registry-based study involving 198 patients with acute promyelocytic leukemia (APL) who underwent autologous hematopoietic cell transplantation (HCT) during second complete remission (CR2) from 1995 to 2012. Arsenic trioxide (ATO) became commercially available in Japan in December 2004, and a substantial increase in the annual numbers of transplantations has occurred since 2005. Patients transplanted after 2006 had significantly better relapse-free and overall survival than those transplanted before 2004 (p = .028 and p = .027, respectively). There was a significant difference in cumulative incidence of relapse in favor of those transplanted after 2006 (p = .008), whereas non-relapse mortality did not differ between the two groups (p = .683). Our findings suggest that the introduction of ATO may have reduced post-transplantation relapse without increasing non-relapse mortality, resulting in significant improvements in overall outcomes for relapsed APL patients undergoing autologous HCT during CR2.

Deficiency of SUMO-specific protease 1 induces arsenic trioxide-mediated apoptosis by regulating XBP1 activity in human acute promyelocytic leukemia

Small ubiquitin-like modifier (SUMO)/sentrin-specific protease 1 (SENP1), a member of the SENP family, is highly expressed in several neoplastic tissues. However, the effect of SENP1 in acute promyelocytic leukemia (APL) has not been elucidated. In the present study, it was observed that SENP1 deficiency had no effect on the spontaneous apoptosis or differentiation of NB4 cells. Arsenic trioxide (As₂O₃) could induce the upregulation of endoplasmic reticulum (ER) stress, resulting in the apoptosis of NB4 cells. Additionally, knockdown of SENP1 significantly increased As₂O₃-induced apoptosis in NB4 cells transfected with small interfering RNA targeting SENP1. SENP1 deficiency also increased the accumulation of SUMOylated X-box binding protein 1 (XBP1), which was accompanied by the downregulation of the messenger RNA expression and transcriptional activity of the XBP1 target genes endoplasmic reticulum-localized DnaJ 4 and Sec61a, which were involved in ER stress and closely linked to the apoptosis of NB4 cells. Taken together, these results revealed that the specific de-SUMOylation activity of SENP1 for XBP1 was involved in the ER stress-mediated apoptosis caused by As₂O₃ treatment in NB4 cells, thus providing insight into potential therapeutic targets for APL treatment via manipulating XBP1 signaling during ER stress by targeting SENP1.

Lyn, a tyrosine kinase closely linked to the differentiation status of primary acute myeloid leukemia blasts, associates with negative regulation of all-trans retinoic acid (ATRA) and dihydroxyvitamin D3 (VD3)-induced HL-60 cells differentiation

Background

Lyn, an import member of Src family kinases (SFKs), is supposed to be implicated in acute myeloid leukemia (AML) pathogenesis and development by participation in AML differentiation, yet the details still remain incompletely understood. The expression status of Lyn and its correlation with multiple clinical parameters including cell differentiation degree, different cytogenetic risk classification, and the activity of myeloperoxidase (MPO) were thus investigated. To address the mechanisms underlying the involvement of Lyn in differentiation induction, the effects of dasatinib, an inhibitor for SFKs including Lyn, on the alterations of all-trans retinoic acid (ATRA)- or dihydroxyvitamin D3 (VD3)-induced differentiation, and c-Myc protein expression were investigated.

Methods

Primary AML blasts were obtained from 31 newly diagnosed AML patients with different French-American-British (FAB) subtypes. The expression of phosphorylated and total Lyn, c-Myc, and CD11b, CD11c and CD15 was analyzed by flow cytometry. The activation of Akt and Erk known to be involved in the regulation of c-Myc expression was investigated using western blotting.

Results

Significant higher expression levels of total Lyn were observed in AML patients with favorable cytogenetics, higher MPO activity and FAB M2 subtype. A clear positive correlation between the expression levels of Lyn and differentiation status of primary AML blasts was observed. Dasatinib inhibited the expression of phosphorylated Lyn, and further enhanced the differentiation-inducing activity of ATRA and VD3 in HL-60 cells. Augmented downregulation of c-Myc protein expression was observed in the combination treatment with ATRA, VD3 and dasatinib compared to treatment with each reagent alone in HL-60 cells. The suppression of the activation of Akt and Erk was also observed concomitantly.

Conclusions

The expression level of total Lyn is closely linked to the differentiation status of AML blasts. The enhancement of differentiation-inducing activity of ATRA/VD3 by dasatinib suggested that Lyn was associated in the negative regulation of ATRA/VD3-induced HL-60 cells differentiation. The enhancement probably was attributed to the downregulation of c-Myc implicated with the suppression of the activation of Akt and Erk. These results provide novel insights into a possible combinational therapeutic approach by targeting Lyn for AML patients, and offer new possibilities for the combination therapy with VD3 and dasatinib.

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.

Acute myeloid leukemia in children: Current status and future directions

Acute myeloid leukemia (AML) accounts for 25% of pediatric leukemia and affects approximately 180 patients annually in Japan. The treatment outcome for pediatric AML has improved through advances in chemotherapy, hematopoietic stem cell transplantation (HSCT), supportive care, and optimal risk stratification. Currently, clinical pediatric AML studies are conducted separately according to the AML subtypes: de novo AML, acute promyelocytic leukemia (APL), and myeloid leukemia with Down syndrome (ML-DS). Children with de novo AML are treated mainly with anthracyclines and cytarabine, in some cases with HSCT, and the overall survival (OS) rate now approaches 70%. Children with APL are treated with an all-trans retinoic acid (ATRA)-combined regimen with an 80-90% OS. Children with ML-DS are treated with a less intensive regimen compared with non-DS patients, and the OS is approximately 80%. HSCT in first remission is restricted to children with high-risk de novo AML only. To further improve outcomes, it will be necessary to combine more accurate risk stratification strategies using molecular genetic analysis with assessment of minimum residual disease, and the introduction of new drugs in international collaborative clinical trials.

New nanoplatforms based on upconversion nanoparticles and single-walled carbon nanohorns for sensitive detection of acute promyelocytic leukemia

New nanoplatforms were prepared by using upconversion nanoparticles as energy donor and single-walled carbon nanohorns as energy acceptor.

Molecular Monitoring as a Path to Cure Acute Promyelocytic Leukemia

Acute promyelocytic leukemia (APL) is a molecularly well-defined disease, characterized by a specific chromosomal translocation; the improvement in biologic and clinical knowledge and subsequent introduction of molecularly targeted therapies have transformed the management of APL, with survival rates now exceeding 80%. Minimal residual disease (MRD) assessment in APL is the most important tool for its treatment; the prognostic role of the molecular detection of promyelocytic leukemia retinoic acid receptor α (PML-RARα) transcript after consolidation therapy in the early identification of the following hematologic relapse is now well established and guides preemptive therapy. First experiences performed with a qualitative polymerase chain reaction (PCR) approach were replaced with more accurate real-time quantitative PCR (RQ-PCR), which guarantees a numeric quantification of MRD. The identification of arsenic trioxide (ATO) as a valid therapy not only in relapsed patients but also as an alternative to standard therapy alone or in association with all-trans-retinoic acid enlarges the setting of validation of MRD evaluation in APL patients, considering a possible different clearance of PML-RARα with innovative therapy different from the standard ones. MRD monitoring demonstrated its validity also in the setting of relapsed patients with interesting results in the autologous and allogeneic stem cell transplantation setting or with the use of other biological agents. The aim of this review is to report and discuss the actual state of the art of MRD in APL.

Introducing minimal residual disease in acute myeloid leukemia

PURPOSE OF REVIEW

Acute myeloid leukemia (AML) is a heterogeneous disease. Detection of minimal residual disease (MRD) has the potential to improve risk stratification, and its routine monitoring may allow timely therapeutic actions such as allogeneic hematopoietic stem cell transplantation. The current review will discuss challenges and available evidence for clinical application of MRD detection in AML management.

RECENT FINDINGS

The heterogeneous nature of AML, variations in genetic aberrations and immunophenotypes among patients and between malignant subclones coexisting within a single patient, is a challenge for the development of a reliable MRD test in AML. MRD value was demonstrated in subtypes of AML in which reliable leukemia-specific genetic marker is present (e.g., core-binding leukemia, AML positive for NPM1 mutation). Multicolor flow cytometry and quantitative PCR monitoring for Wilms tumor 1 gene transcript have also been shown to correlate with disease progression. MRD results should always be interpreted within patient-specific clinical context considering other risk factors and timing of MRD eradication.

SUMMARY

Introduction of MRD testing into routine clinical practice is a challenge in AML. An improvement in laboratory techniques along with identification of additional leukemia-specific markers is required.

Arsenic trioxide and all-trans retinoic acid treatment for acute promyelocytic leukaemia in all risk groups (AML17): results of a randomised, controlled, phase 3 trial

BACKGROUND

Acute promyelocytic leukaemia is a chemotherapy-sensitive subgroup of acute myeloid leukaemia characterised by the presence of the PML-RARA fusion transcript. The present standard of care, chemotherapy and all-trans retinoic acid (ATRA), results in a high proportion of patients being cured. In this study, we compare a chemotherapy-free ATRA and arsenic trioxide treatment regimen with the standard chemotherapy-based regimen (ATRA and idarubicin) in both high-risk and low-risk patients with acute promyelocytic leukaemia.

METHODS

In the randomised, controlled, multicentre, AML17 trial, eligible patients (aged ≥16 years) with acute promyelocytic leukaemia, confirmed by the presence of the PML-RARA transcript and without significant cardiac or pulmonary comorbidities or active malignancy, and who were not pregnant or breastfeeding, were enrolled from 81 UK hospitals and randomised 1:1 to receive treatment with ATRA and arsenic trioxide or ATRA and idarubicin. ATRA was given to participants in both groups in a daily divided oral dose of 45 mg/m(2) until remission, or until day 60, and then in a 2 weeks on-2 weeks off schedule. In the ATRA and idarubicin group, idarubicin was given intravenously at 12 mg/m(2) on days 2, 4, 6, and 8 of course 1, and then at 5 mg/m(2) on days 1-4 of course 2; mitoxantrone at 10 mg/m(2) on days 1-4 of course 3, and idarubicin at 12 mg/m(2) on day 1 of the final (fourth) course. In the ATRA and arsenic trioxide group, arsenic trioxide was given intravenously at 0·3 mg/kg on days 1-5 of each course, and at 0·25 mg/kg twice weekly in weeks 2-8 of course 1 and weeks 2-4 of courses 2-5. High-risk patients (those presenting with a white blood cell count >10 × 10(9) cells per L) could receive an initial dose of the immunoconjugate gemtuzumab ozogamicin (6 mg/m(2) intravenously). Neither maintenance treatment nor CNS prophylaxis was given to patients in either group. All patients were monitored by real-time quantitative PCR. Allocation was by central computer minimisation, stratified by age, performance status, and de-novo versus secondary disease. The primary endpoint was quality of life on the European Organisation for Research and Treatment of Cancer (EORTC) QLQ-C30 global health status. All analyses are by intention to treat. This trial is registered with the ISRCTN registry, number ISRCTN55675535.

FINDINGS

Between May 8, 2009, and Oct 3, 2013, 235 patients were enrolled and randomly assigned to ATRA and idarubicin (n=119) or ATRA and arsenic trioxide (n=116). Participants had a median age of 47 years (range 16-77; IQR 33-58) and included 57 high-risk patients. Quality of life did not differ significantly between the treatment groups (EORTC QLQ-C30 global functioning effect size 2·17 [95% CI -2·79 to 7·12; p=0·39]). Overall, 57 patients in the ATRA and idarubicin group and 40 patients in the ATRA and arsenic trioxide group reported grade 3-4 toxicities. After course 1 of treatment, grade 3-4 alopecia was reported in 23 (23%) of 98 patients in the ATRA and idarubicin group versus 5 (5%) of 95 in the ATRA and arsenic trioxide group, raised liver alanine transaminase in 11 (10%) of 108 versus 27 (25%) of 109, oral toxicity in 22 (19%) of 115 versus one (1%) of 109. After course 2 of treatment, grade 3-4 alopecia was reported in 25 (28%) of 89 patients in the ATRA and idarubicin group versus 2 (3%) of 77 in the ATRA and arsenic trioxide group; no other toxicities reached the 10% level. Patients in the ATRA and arsenic trioxide group had significantly less requirement for most aspects of supportive care than did those in the ATRA and idarubicin group.

INTERPRETATION

ATRA and arsenic trioxide is a feasible treatment in low-risk and high-risk patients with acute promyelocytic leukaemia, with a high cure rate and less relapse than, and survival not different to, ATRA and idarubicin, with a low incidence of liver toxicity. However, no improvement in quality of life was seen.

A molecular risk score integrating BAALC, ERG and WT1 expression levels for risk stratification in acute promyelocytic leukemia

To date risk stratification in acute promyelocytic leukemia (APL) is based on highly dynamic leukocyte and platelet counts only. To identify a more robust risk stratification model, a molecular risk score was developed based on expression levels of the genes BAALC, ERG and WT1. Hereby, the main focus was on prediction of relapse. The integrative risk score divided patients into two groups with highly significant differences in outcome. It discriminated a high risk group with a high incidence of relapse successfully from a low risk group with no APL-related events after achievement of first remission. Especially the concurrent presence of molecular risk factors showed to be a negative prognostic factor in APL. The molecular risk score might be a promising approach to guide monitoring of APL patients and therapeutic decisions in the future.

Granulocyte colony-stimulating factor potentiates all-trans retinoic acid-induced granulocytic differentiation in acute promyelocytic leukemia cell line HT93A

BACKGROUND

Granulocyte colony-stimulating factor (G-CSF) promotes proliferation, survival, and differentiation of myeloid-linage leukemic cells, as well as normal hematopoietic cells. Terminal granulocytic differentiation can be induced in acute promyelocytic (APL) cell line HT93A by G-CSF and all-trans retinoic acid (ATRA). Because the detailed mechanism has never been shown, we investigated the signal transduction pathway in granulocytic differentiation by G-CSF, alone or in combination with ATRA.

METHODS

HT93A cell viability and growth were investigated by trypan blue exclusion assay. Cell differentiation was assessed by CD11b and CD34 expressions. Intracellular protein expressions were also evaluated by flow cytometry after fixation and permeabilization.

RESULTS

ATRA (100 nM) induced granulocytic differentiation (upregulation of CD11b and downregulation of CD34) and the effect was potentiated by addition of G-CSF, while G-CSF alone had no effect on HT93A cells. The addition of G-CSF to ATRA had little or no effect on NB4 and THP-1 cells in comparison to ATRA alone. G-CSF receptor expression was reduced by ATRA treatment in a time-dependent manner. After 5 days' incubation with ATRA, the expression levels of signal transducer and activator of transcription (STAT) 3, and phosphorylated STAT3 and STAT5, were significantly reduced. STAT5 was strongly activated by G-CSF stimulation in ATRA-pretreated cells in comparison to untreated cells. In contrast, STAT3 showed no response to G-CSF. Janus kinase (JAK) inhibitor ruxolitinib (320 nM) had little or no effect on ATRA-induced differentiation, but eliminated the enhancing effect of G-CSF, as evidenced by the levels of CD11b and CD34 expression. These results suggest G-CSF activates STAT5 through the JAK pathway in combination with ATRA, resulting in myeloid differentiation in HT93A cells.

CONCLUSIONS

In conclusion, activation of the JAK-STAT pathway is likely essential for inducting differentiation in the APL cell line HT93A; thus, monitoring its expression and activation is important for predicting clinical efficacy and understanding the mechanisms of cytokine-dependent myelopoiesis, proliferation, and differentiation of acute myeloid leukemia.

Minimal residual disease testing in hematologic malignancies and solid cancer

Minimal residual disease (MRD) assays are of a great value to assess treatment efficacy and may provide prognostic information. This is particularly relevant in the era of targeted therapy where the introduction of MRD monitoring has fundamentally transformed the way in which cancer patients are managed. While MRD guidelines are well-established for chronic myeloid leukemia, acute promyelocytic leukemia and acute lymphoblastic leukemia, areas for continuing development are available. High level of standardization and regular external quality control rounds and recommendations for data interpretation remain essential to improve MRD monitoring. In this review, we describe the different applications of MRD assays in most frequent hematologic malignancies and solid cancer and provide an overview of the strengths and potential weaknesses of each method.

Retinal toxicities of cancer therapy drugs: biologics, small molecule inhibitors, and chemotherapies

PURPOSE

To review reported retinal side effects from current cancer therapy drugs.

METHODS

Retinal toxicities from ophthalmologic or oncologic case reports, case series, and clinical trials were identified by a systematic literature search using Lexicomp and PubMed.

RESULTS

Four biologics, 8 small molecule inhibitors, and 17 traditional chemotherapy agents had reported retinal side effects. For biologics, interferon alpha 2b was associated with retinopathy, denileukin diftitiox with pigmentary retinopathy, ipilimumab with a Vogt-Koyanagi-Harada-like syndrome, and trastuzumab with retinal ischemia. For small molecule inhibitors, v-raf murine sarcoma viral oncogene homolog B (BRAF) inhibitors were associated with uveitis, mitogen-activated protein kinase/extracellular signal-regulated kinase inhibitors with pigment epithelium detachments, and tyrosine kinase inhibitors with macular edema. Steroid antagonists were associated with crystalline retinopathy and macular edema. Nitrosoureas, platinum analogs, and cytosine arabinoside were associated with retinal vascular occlusions. Antimicrotubular agents were associated with cystoid macular edema but without fluorescein leakage. Retinoic acid derivatives were associated with impaired night vision, and mitotane was associated with a pigmentary retinopathy and papilledema.

CONCLUSION

Certain agents used in the treatment of systemic cancer are associated with ocular complications. Awareness of these complications will allow early detections and maybe reversal of some of the ocular problems.

Tamibarotene As Maintenance Therapy for Acute Promyelocytic Leukemia: Results From a Randomized Controlled Trial

Purpose

The introduction of all-trans-retinoic acid (ATRA) has significantly improved outcomes for acute promyelocytic leukemia (APL), although a subset of patients still suffer relapse. The purpose of this study was to evaluate the role of maintenance therapy with the synthetic retinoid tamibarotene in APL.

Patients and Methods

Patients with newly diagnosed APL in molecular remission at the end of consolidation therapy were randomly assigned to receive ATRA or tamibarotene, both orally, for 14 days every 3 months for up to 2 years.

Results

A total of 347 patients were enrolled. Of the 344 eligible patients, 319 (93%) achieved complete remission. After completing three courses of consolidation therapy, 269 patients underwent maintenance random assignment. The relapse-free survival (RFS) rate at 4 years was 84% for the ATRA arm and 91% for the tamibarotene arm (hazard ratio [HR], 0.54; 95% CI, 0.26 to 1.13). When the analysis was restricted to 52 high-risk patients with an initial WBC count ≥ 10.0 × 109/L, the intergroup difference was statistically significant, with 4-year RFS rates of 58% for the ATRA arm and 87% for the tamibarotene arm (HR, 0.26; 95% CI, 0.07 to 0.95). For patients with non–high-risk disease, the HR was 0.82 (95% CI, 0.32 to 2.01). The test for interaction between treatment effects and these subgroups resulted in P = .075. Both treatments were generally well tolerated.

Conclusion

In this trial, no difference was detected between ATRA and tamibarotene for maintenance therapy. In an exploratory analysis, there was a suggestion of improved efficacy of tamibarotene in high-risk patients, but this requires further study.