Acute promyelocytic leukaemia: epidemiology and risk factors. A report of the GIMEMA Italian archive of adult acute leukaemia. GIMEMA Cooperative Group

Acute Promyelocytic Leukemia in the Real World: Understanding Outcome Differences and How We Can Improve Them

The advent of all-trans retinoic acid (ATRA) and arsenic trioxide (ATO) has revolutionized the treatment of acute promyelocytic leukemia (APL), resulting in excellent rates of remission and long-term survival. However, real-world outcomes often fall short of those observed in clinical trials due to various factors related to patient demographics and clinical practices. This review examines APL treatment outcomes in real-world settings and highlights the phenomenon of APL clusters. Clinical trials frequently exclude older patients and individuals with significant comorbidities, yet these groups represent a substantial portion of patients in clinical practice. Early mortality remains high in real-world settings, compounded by delayed diagnosis and treatment initiation, as well as the inexperience of some community providers and limited resources of their centers in managing APL and its associated complications. High rates of disease and induction-related complications further exacerbate early mortality. Continuous education and collaboration between community healthcare centers and expert institutions are essential, and international partnerships between resource-limited settings and expert centers can improve global APL outcomes. Ongoing monitoring for measurable residual disease (MRD) recurrence and long-term treatment toxicity, coupled with comprehensive patient evaluations, and experienced management, can enhance long-term outcomes. The clustered incidence of APL, while frequently reported, remains poorly understood. Regular reporting of these clusters could provide valuable insights into disease pathology and aid in developing predictive models for APL incidence, which would guide future resource allocation.

Frontline treatment of acute myeloid leukemia in adults

Recent years have highlighted significant progress in understanding the underlying genetic and epigenetic signatures of acute myeloid leukemia(AML). Most importantly, novel chemotherapy and targeted strategies have led to improved outcomes in selected genetic subsets. AML is a remarkably heterogeneous disease, and individualized therapies for disease-specific characteristics (considering patients' age, cytogenetics, and mutations) could yield better outcomes. Compared with the historical 5-to 10-year survival rate of 10%, the survival of patients who undergo modern treatment approaches reaches up to 40-50%, and for specific subsets, the improvements are even more dramatic; for example, in acute promyelocytic leukemia, the use of all-trans retinoic acid and arsenic trioxide improved survival from 30 to 40% up to 80 to 90%. Similar progress has been documented in core-binding-factor-AML, with an increase in survival from 30% to 80% upon the use of high-dose cytarabine/fludarabine/granulocyte colony-stimulating factor combination regimens. AML treatment was also recently influenced by the discovery of the superiority of regimens with higher dose Ara-C and nucleoside analogues compared with the "7+3"regimen, with about a 20% improvement in overall survival. Despite these significant differences, most centers continue to use the "7+3" regimen, and greater awareness will improve the outcome. The discovery of targetable molecular abnormalities and recent studies of targeted therapies (gemtuzumab ozagomycin, FLT3 inhibitors, isocitrate dehydrogenase inhibitors, and epigenetic therapies), future use of checkpoint inhibitors and other immune therapies such as chimeric antigen receptor T-cells, and maintenance strategies based on the minimal residual disease evaluation represent novel, exciting clinical leads aimed to improve AML outcomes in the near future.

Global characteristics of childhood acute promyelocytic leukemia

Acute promyelocytic leukemia (APL) comprises approximately 5-10% of childhood acute myeloid leukemia (AML) cases in the US. While variation in this percentage among other populations was noted previously, global patterns of childhood APL have not been thoroughly characterized. In this comprehensive review of childhood APL, we examined its geographic pattern and the potential contribution of environmental factors to observed variation. In 142 studies (spanning >60 countries) identified, variation was apparent-de novo APL represented from 2% (Switzerland) to >50% (Nicaragua) of childhood AML in different geographic regions. Because a limited number of previous studies addressed specific environmental exposures that potentially underlie childhood APL development, we gathered 28 childhood cases of therapy-related APL, which exemplified associations between prior exposures to chemotherapeutic drugs/radiation and APL diagnosis. Future population-based studies examining childhood APL patterns and the potential association with specific environmental exposures and other risk factors are needed.

The impact of medical education and networking on the outcome of leukemia treatment in developing countries. The experience of International Consortium on Acute Promyelocytic Leukemia (IC-APL)

OBJECTIVES

Several clinical trials conducted in Europe and US reported favorable outcomes of patients with APL treated with the combination of all trans retinoic acid (ATRA) and anthracyclines. Nevertheless, the results observed in developing countries with the same regimen was poorer, mainly due to high early mortality mainly due bleeding. The International Consortium on Acute Promyelocytic Leukemia (IC-APL) is an initiative of the International Members Committee of the ASH and the project aims to reduce this gap through the establishment of international network, which was launched in Brazil, Mexico and Uruguay.

METHODS

The IC-APL treatment protocol is similar to the PETHEMA 2005, but changing idarubicin to daunorubicin. All patients with a suspected diagnosis of APL were immediately started on ATRA, while bone marrow samples were shipped to a national central lab where genetic verification of the diagnosis was performed. The immunofluorescence using an anti-PML antibody allowed a rapid confirmation of the diagnosis and, the importance of supportive measures was reinforced.

RESULTS

The interim analysis of 97 patients enrolled in the IC-APL protocol showed that complete remission (CR) rate was 83% and the 2-year overall survival and disease-free survival were 80% and 90%, respectively. Of note, the early mortality rate was reduced to 7.5%.

DISCUSSION

The results of IC-APL demonstrate the impact of educational programs and networking on the improvement of the leukemia treatment outcome in developing countries.

Epidemiology and treatment of acute promyelocytic leukemia in latin america

Distinct epidemiological characteristics have been described in Acute Promielocytic Leukemia (APL). Populations from Latin America have a higher incidence of APL and in some geographic areas a distinct distribution of the PML-RARA isoforms is present. Here, we review the main differences in APL epidemilogy in Latin America as well as treatment outcomes.

Geographic differences in the incidence of cytogenetic abnormalities of acute myelogenous leukemia (AML) in Spain

The incidence of chromosomal abnormalities in acute myeloid leukemia (AML) differs according to geographical regions in Spain. We analyse 1,271 consecutive patients diagnosed of AML between 1995 and 2002 in three different regions of Spain: northern, central and southern. There were 624 males (55%) and 505 females (45%). Age ranged between 1 month and 94 years with a median of 61 years. Abnormal karyotypes were observed in 64% of cases. Numerical abnormalities as sole cytogenetic changes were detected in 15% of patients, while structural aberrations were present in 28% of cases, and both abnormalities were found in 22% of patients. A significantly higher proportion of t(15;17) was observed in the south of Spain (21.6%) than in the central (17%) or northern regions (12.6%) (p=0.03). By contrast, patients from the south of Spain showed lower incidence of t(8;21) (0%, compared to 1.6% and 3.6% in central and northern areas, respectively, p=0.04). These differences were maintained in the age-adjusted analysis. Trisomy 8 showed similar incidence in southern and central areas, while the incidence in the northern area was lower (14% and 10%, respectively, p=0.04). Other chromosomal abnormalities, such as inv(16) or 11q23 rearrangements, were found at similar frequencies in the three regions.

A highly unusual cluster of acute promyelocytic leukaemia: an environmental aetiology?

We report three consecutive cases of acute promyelocytic leukaemia (APML) that were diagnosed within a 4-month period. This unexpected sequence of events was made all the more notable following our discovery of co-incidental geographic, social, and occupational factors that linked them together. Our data strongly suggests that environmental agents may play a greater role in the aetiology of APML than is commonly perceived.

The epidemiology of acute promyelocytic leukaemia

Recent progress has demonstrated that acute myelogenous leukaemia (AML) can be classified by chromosomal aberrations and leukaemia-specific molecular gene rearrangements into homogeneous biological subgroups. However, descriptive epidemiological reports on AML consider the disease as a single entity. Acute promyelocytic leukaemia (APL) is an example of a truly unique AML subtype that has an easy-to-recognize morphology associated uniformly with distinct chromosomal and gene rearrangement aberration. Thus, APL is amenable to epidemiological studies as a model of human AML with a specific and well-characterized chromosomal and molecular abnormality. This chapter shows that epidemiological characteristics of APL are different from those of non-APL AML using data from the Los Angeles tumour registry and other sources. The principal distinct APL epidemiological features that so far have been described are the constant incidence with age after age 20, equal incidence in males and females and higher frequency among patients originating in Latin America. The APL-specific PML/RARalpha gene rearrangement is different in Latinos and non-Latinos. Therapy-related APL has the same response to treatment and outcome as de novo APL. It is therefore likely that aetiological factors for APL are different from those of other AML subtypes. So far no environmental and/or occupational risk factors have been found for APL. Future molecular studies of the APL-specific fusion gene combined with epidemiological and environmental investigations might lead to better understanding of specific aetiological factors in APL patients.

Antigen expression patterns reflecting genotype of acute leukemias

Multi-parameter flow cytometry, molecular genetics, and cytogenetic studies have all contributed to new classification of leukemia. In this review we discuss immunophenotypic characteristics of major genotypic leukemia categories. We describe immunophenotype of: B-lineage ALL with MLL rearrangements, TEL/AML1, BCR/ABL, E2A/PBX1 translocations, hyperdiploidy, and myc fusion genes; T-ALL with SCL gene aberrations and t(5;14) translocation; and AML with AML1/ETO, PML/RARalpha, OTT/MAL and CBFbeta/MYH11 translocations, trisomies 8 or 11 and aberrations of chromosomes 7 and 5. Whereas some genotypes associate with certain immunophenotypic features, others can present with variable immunophenotype. Single molecules (as NG2, CBFbeta/SMMHC and PML/RARalpha proteins) associated with or derived from specific translocations have been described. More often, complex immunophenotype patterns have been related to the genotype categories. Most known associations between immunophenotype and genotype have been defined empirically. Therefore, these associations should be validated in independent patient cohorts before they can be widely used for prescreening of leukemia. Progress in our knowledge on leukemia will show how the molecular-genetic changes modulate the immunophenotype as well as how the expressed protein molecules further modulate cell behavior.