Table of contents
Acute promyelocytic leukemia
Background
Overview
Definition
APL is a distinct subtype of acute myeloid leukemia characterized by a chromosomal abnormality involving translocation between chromosomes 15 and 17.
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Pathophysiology
APL is caused by a balanced reciprocal translocation of chromosomes 15 and 17, which involves the retinoic acid receptor alpha gene on chromosome 17 and the promyelocytic leukemia gene on chromosome 15.
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Epidemiology
The incidence of APL in Europe is estimated at 0.11 per 100,000 person-years, accounting for 10-15% of acute myeloid leukemia cases.
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Disease course
APL can present in a similar manner as those with other subtypes of acute myeloid leukemia. This includes symptoms of pancytopenia, such as easy fatigue, weakness, infections, and/or bleeding complications. Bone marrow packed with abnormal promyelocytes not only contributes to blood cell count abnormalities but also provokes a unique, severe coagulopathy with elements of both DIC and primary fibrinolysis. This coagulopathy can lead to severe bleeding events, including intracranial bleeding.
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Prognosis and risk of recurrence
Historically APL had a fatal outcome, but recent advances in treatment regimens, especially all-trans retinoic acid-based regimens, have drastically improved treatment outcomes, with complete remission rates approaching 100% and event-free survival rates > 90%.
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Guidelines
Key sources
The following summarized guidelines for the evaluation and management of acute promyelocytic leukemia are prepared by our editorial team based on guidelines from the European Society of Medical Oncology (ESMO 2020), the International Society on Thrombosis and Haemostasis (ISTH 2020,2015), the European Leukemia Net (ELN 2019), and the College of American Pathologists (CAP/ASH 2017).
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Diagnostic investigations
Mutational analysis: as per ELN 2019 guidelines, obtain molecular testing for the detection of PML-RARA fusion (or rare molecular variants) to confirm the diagnosis of APL.
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Coagulation studies
Diagnostic procedures
Immunostaining: as per ELN 2019 guidelines, consider obtaining immunostaining with anti-promyelocytic leukemia antibodies (in addition to FISH, reverse transcriptase PCR, real-time quantitative PCR, reverse transcription-quenching loop-mediated isothermal amplification) for rapid diagnosis of APL.
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Medical management
General principles: as per ELN 2019 guidelines, manage the diagnosis of APL (once suspected) as a medical emergency.
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Initial therapy
Consolidation therapy
Maintenance therapy
Management of coagulopathy
Management of differentiation syndrome
Therapeutic procedures
Specific circumstances
Pediatric patients: as per ELN 2019 guidelines, administer all-trans retinoic acid at a dose of 25 mg/m²/day in pediatric and adolescent patients.
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Pregnant patients
Elderly patients
Patients with comorbidities
Preventative measures
Follow-up and surveillance
Treatment monitoring: as per ELN 2019 guidelines, interpret an increase of WBC counts > 10×10⁹/L after treatment initiation with all-trans retinoic acid and/or arsenic trioxide as a sign of all-trans retinoic acid/arsenic trioxide-induced differentiation and do not reclassify the patient as having high-risk disease.
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Management of relapsed/refractory disease