Hematopoietic cell transplantation in acute promyelocytic leukemia: a comprehensive review

Allogeneic stem cell transplantation for advanced acute promyelocytic leukemia in the ATRA and ATO era

The role of allogeneic stem cell transplant in advanced acute promyelocytic leukemia patients who received standard first- and second-line therapy is still unknown. We report the outcome of 31 acute promyelocytic leukemia patients (median age 39 years) who underwent allogeneic transplant in second remission (n=15) or beyond (n=16). Sixteen patients were real-time polymerase chain reaction positive and 15 negative for PML/RARA pre-transplant. The 4-year overall survival was 62% and 31% for patients transplanted in second remission and beyond, respectively (P=0.05), and 64% and 27% for patients with pre-transplant negative and positive real-time polymerase chain reaction, respectively (P=0.03). The 4-year cumulative incidence of relapse was 32% and 44% for patients transplanted in second remission and beyond, respectively (P=0.37), and 30% and 47% for patients transplanted with negative and positive real-time polymerase chain reaction, respectively (P=0.30). Transplant-related mortality was 19.6%. In conclusion, allogeneic transplant is effective in advanced acute promyelocytic leukemia in the all-trans-retinoic acid and arsenic trioxide era, and should be considered once relapse is diagnosed.

Pathogenesis and treatment of leukemia: an Asian perspective

INTRODUCTION

Leukemias occur worldwide, but there are important geographic differences in incidences.

AREAS COVERED

Three leukemias with special Asian perspectives, acute promyelocytic leukemia (APL), T-cell large granular lymphocyte (T-LGL) leukemia and NK-cell leukemia.

EXPERT OPINION

In APL, China has made contributions in discovering the efficacy of all-trans retinoic acid (ATRA) and arsenic trioxide. Some APL patients are potentially curable after treatment with ATRA or arsenic trioxide as a single agent. Combined treatment of APL with ATRA and arsenic trioxide induces remission with deeper molecular response. An oral formulation of arsenic trioxide is available, making outpatient treatment feasible. Future regimens for APL should examine how ATRA and arsenic trioxide can be optimally combined with other synergistic drugs. Asian patients with T-LGL leukemia present more frequently with pure red cell aplasia, but less frequently with neutropenia, recurrent infection, splenomegaly and rheumatoid arthritis as compared with Western patients. These differences have potential effects on treatment and disease pathogenesis. NK-cell leukemia is rapidly fatal and occurs almost exclusively in Asian and South American patients. Conventional anthracycline-based chemotherapy designed for B-cell lymphomas do not work in NK-cell leukemias. Novel therapeutic approaches targeting cellular signaling pathways or preferentially upregulated genes are needed to improve outcome.

Advances in therapies for acute promyelocytic leukemia

Acute promyelocytic leukemia (APL), a distinct subtype of acute myelogenous leukemia (AML), results from the arrest of the maturation of hematopoietic progenitors at the promyelocyte stage. It has been shown that APL is associated with a reciprocal chromosomal translocation, involving chromosomes 15 and 17, which fuses the gene encoding the retinoic acid receptor α (RARα) and the promyelocytic leukemia (PML) gene. The resultant PML-RARα fusion protein plays a critical role in the pathogenesis of APL. Although there are many subtypes of AML, all are typically managed using a standard chemotherapy regimen of an anthracycline plus cytarabine arabinoside (CA). Despite high rates of complete remission following standard chemotherapy, most patients relapse and long-term disease-free survival is only 30-40%. The introduction of drugs such as all-trans retinoic acid (ATRA) that promote progenitor differentiation by directly inhibiting the PML-RARα fusion protein has changed the treatment paradigm for APL and markedly improved patient survival. The purposes of the present review are to provide the latest results and future directions of clinical research into APL and to illustrate how new therapies, such as ATRA plus anthracycline-based induction and consolidation therapy, risk-adapted therapy, salvage therapy containing arsenic trioxide-based regimens, and hematopoietic stem cell transplantation, have improved the treatment outcomes for APL patients.

Incidence of extramedullary disease in patients with acute promyelocytic leukemia: a single-institution experience

Using current treatment regimens, over 90% of patients with acute promyelocytic leukemia will achieve complete remission (CR). However, approximately 30% of these patients will relapse, including a small proportion who will develop extramedullary disease (EMD). In this study, we investigated the incidence of EMD in 263 patients with APL who were treated at our institution from January 1990 to May 2008. With a median follow-up of 31 months (range 2 days-203 months), 8 (3%) patients developed EMD. The most commonly affected site was the central nervous system (n = 7). Before developing EMD, one patient had achieved CR with a chemotherapy-only regimen, six patients had achieved CR with all-trans-retinoic acid (ATRA)-based regimens, and one patient had achieved CR with an ATRA plus arsenic trioxide (ATO)-based regimen. The EMD conferred a poor prognosis; five patients died within 4 months of developing EMD. The molecular status did not predict EMD; four patients had a negative PCR for the PML-RARA transcripts prior to relapse with EMD. In conclusion, the incidence of EMD is low. We were unable to identify any specific factors that could predict the development of EMD.

Arsenic trioxide

BACKGROUND

The ancient drug, arsenic, has remarkable efficacy in the treatment of relapsed acute promyelocytic leukemia (APL) and this success has led to exploration of its use in other malignancies.

OBJECTIVE

To provide an overview of the mechanism of action of arsenic and summarize its development in the treatment of APL and other malignant disorders.

METHODS

A 20-year search of MEDLINE, EMBASE and Web of Science was conducted.

RESULTS/CONCLUSIONS

A series of clinical trials with arsenic trioxide has confirmed its benefit in the therapy of APL. Its role in the treatment of other malignancies remains to be determined. Careful attention to the clinical management of patients on arsenic trioxide therapy can significantly lessen the risk of major side effects.