Differentiation Syndrome and Early Mortality in Patients with Acute Promyelocytic Leukemia (APL) Treated with All-Trans Retinoic Acid

Abstract

Acute promyelocytic leukaemia went from the most rapidly fatal form of leukaemia to the most curable within a decade, and the drug responsible brought its own lethal complication with it. Differentiation syndrome and early haemorrhagic death together account for almost all the mortality that remains in a disease with long-term survival above 80 per cent. Objectives: To review the published evidence on differentiation syndrome and early mortality in acute promyelocytic leukaemia treated with all-trans retinoic
acid: how often each occurs, which patients are at risk, what corticosteroid prophylaxis achieves, and why reported figures vary so widely. Material and Methods: Narrative review of cooperative group trials, registry analyses, single-centre cohorts and expert recommendations indexed in PubMed and the major haematology journals. Studies were eligible if they reported the incidence, risk factors or outcome of differentiation syndrome, or early mortality, in a defined population with acute promyelocytic leukaemia. No new patient data were generated and no patients were recruited; every estimate quoted is one published by the original investigators.
Results: Reported incidence of differentiation syndrome ranges from 17.8 to 62.4 per cent across cohorts, with around 25 to 30 per cent in the largest adult series. In 739 patients treated on two consecutive cooperative group protocols, severe but not moderate syndrome increased mortality, incidence was bimodal with peaksin the first and third weeks of therapy, and a white cell count above 5 x 109/L together with an abnormal serum creatinine predicte dsevere disease. Corticosteroid prophylaxis reduced the odds of differentiation syndrome by roughly ninety per cent (OR 0.10, 95% CI 0.03-0.35). Early death remains the dominant residual problem: a registry analysis of 1,400 patients reported 17.3 per cent, rising with age, against 13.5 per cent in a trial-treated cohort. A peak white cell count above
43 x 109/L predicted both early death and differentiation syndrome better than the count at diagnosis, including among patients classified as low risk. Conclusion: The count that matters is the peak reached during induction rather than the one measured at diagnosis, which means risk stratification performed once at presentation misses patients who declare themselves over the following week. Corticosteroid prophylaxis is the intervention with the clearest effect and remains inconsistently applied. Abbreviations: APL – Acute Promyelocytic Leukaemia, ATRA – All-Trans Retinoic Acid, ATO – Arsenic Trioxide, DS – Differentiation Syndrome,
PML-RARA – Promyelocytic Leukaemia-Retinoic Acid Receptor Alpha, WBC – White Blood Cell Count, WBCdx – White Cell Count at Diagnosis, WBCmax – Peak White Cell Count, DIC – Disseminated Intravascular Coagulation, ICH – Intracranial Haemorrhage, CR – Complete Remission, OR – Odds Ratio.