OBJECTIVES: Acute myeloid leukemia (AML) with 20–29% blasts is prognostically distinct from AML with ≥30% blasts (AML≥30), with a clinical course similar to that of myelodysplastic syndrome (MDS) with 10–19% blasts. This systematic review aimed to evaluate the global epidemiology of patients with AML with 20–29% blasts.

METHODS: MEDLINE, EMBASE, the Cochrane library, and grey literature were searched for observational studies published between 1/1/2008–10/7/2020. Eligible publications written in English reported incidence or prevalence of AML among patients ≥18 years old.

RESULTS: The review identified 44 studies, with four focusing on AML (20–29% blasts).

AML prevalence ranged from 1.5–13.7 per 100,000. Global incidence of AML was 1.54/100,000 in 2017, with an increasing trend with age. Between 2017–2020, age-adjusted AML incidence ranged from 2.58/100,000 in Spain to 4.3/100,000 in the US.

In a population-based study from Poland, AML (20–29% blasts) incidence (males/females) was 0.1/0.2 per 100,000 person-years in 2012. In three retrospective hospital-based studies, 17–34% of incident AML cases were AML (20–29% blasts).

Three studies compared AML (20–29% blasts) and AML≥30. Hypomethylating agents were more frequently used to treat AML with 20–29% blasts versus AML≥30 (23–35% versus 0–18%), and chemotherapy (high-or low-intensity therapy) was less frequently used to treat AML with 20–29% blasts versus AML≥30 (44–58% versus 59–99%). Median survival from diagnosis ranged from 16–21 months (AML with 20–29% blasts) versus 12–25 months (AML≥30).

CONCLUSIONS: AML is a rare disease with poor prognosis. Observed scarcity of data on epidemiology and prognosis of AML with 20–29% blasts may be due to poor reporting of blast count percentages in published literature. Differences in patient outcomes and treatment choice between AML (20–29% blasts) and AML≥30 suggest additional research is warranted for disease characterization.