Acute promyelocytic leukemia: where did we start, where are we now, and the future

Abstract

Historically, acute promyelocytic leukemia (APL) was considered to be one of the most fatal forms of acute leukemia with poor outcomes before the introduction of the vitamin A derivative all-trans retinoic acid (ATRA). With considerable advances in therapy, including the introduction of ATRA initially as a single agent and then in combination with anthracyclines, and more recently by development of arsenic trioxide (ATO)-containing regimens, APL is now characterized by complete remission rates of 90% and cure rates of ∼80%, even higher among low-risk patients. Furthermore, with ATRA-ATO combinations, chemotherapy may safely be omitted in low-risk patients. The disease is now considered to be the most curable subtype of acute myeloid leukemia (AML) in adults. Nevertheless, APL remains associated with a significant incidence of early death related to the characteristic bleeding diathesis. Early death, rather than resistant disease so common in all other subtypes of AML, has emerged as the major cause of treatment failure.

Figure 1

Relapse-free survival curves for APML4, the phase 2 trial utilizing combination of ATRA, ATO, and idarubicin in newly diagnosed APL. Panel a comprises all patients on APML4 (n=112) and panel b stratifies patients by Sanz risk category.

Figure 2

EFS probability and CIR in non-high-risk APL patients on Italian–German APL 0406 trial comparing ATRA–ATO with ATRA–chemotherapy on the extended final series.

Figure 3

Overall survival curves for phase 3 randomized noninferiority trial comparing oral ATO (realgar-indigo naturalis formula (RIF) with i.v. ATO.