Tracy Murphy

INTRODUCTION: Acute myeloid leukemia (AML) is the most common acute forms of leukemia in adults. It has a poor long-term survival with a high relapse rate and at relapse, is commonly resistant to available therapies. The current combination of daunorubicin (DNR) for three days and cytarabine (Ara-C) as a continuous infusion for seven days, more commonly known as '3 + 7' has remained essentially unaltered over the last forty-four years and remains the standard induction regimen internationally. Areas covered: This paper will briefly review clinically important trials related to '3 + 7'. Somatic mutations in AML that are linked to chemoresistance to '3 + 7'will be discussed. Other topics covered include the novel ratiometric agent containing daunorubicin and cytarabine, CPX-351, and midostaurin in FLT3 mutated AML. Expert opinion: '3 + 7' continues to be the backbone of therapy for AML. However, genetic risk stratification should be used to determine patients who are unlikely to respond to standard intensive chemotherapy and hence, should be enrolled onto a clinical trial upfront. This will facilitate development of newer effective treatment strategies in AML. Patients with mutations that are associated with chemoresistance should be offered therapies which may circumvent or overcome these pathways.

Core-binding factor acute myeloid leukemia is characterized by t(8;21) or inv(16) and the fusion proteins RUNX1-RUNX1T1 and CBFB-MYH11. International guidelines recommend monitoring for measurable residual disease every 3 months for 2 years after treatment. However, it is unknown if serial molecular monitoring can predict and prevent morphologic relapse. We conducted a retrospective single-center study of 114 patients in complete remission who underwent molecular monitoring with RT-qPCR of RUNX1-RUNX1T1 or CBFB-MYH11 transcripts every 3 months. Morphologic relapse was defined as re-emergence of >5% blasts and molecular relapse as ≥1 log increase in transcript level between 2 samples. Over a median follow-up time of 3.7 years (range 0.2-14.3), remission persisted in 71 (62.3%) patients but 43 (37.7%) developed molecular or morphologic relapse. Patients who achieved <3 log reduction in RUNX1-RUNX1T1 or CBFB-MYH11 transcripts at end of chemotherapy had a significantly higher risk of relapse compared to patients who achieved ≥3 log reduction (61.1% vs. 33.7%, p=0.004). The majority of relapses (74.4%, n=32) were not predicted by molecular monitoring and occurred rapidly with <100 days from molecular to morphologic relapse. Molecular monitoring enabled the detection of impending relapse and permitted pre-emptive intervention prior to morphologic relapse in only 11 (25.6%) patients. The current practice of molecular monitoring every 3 months provided insufficient lead-time to identify molecular relapses and prevent morphologic relapse in the majority of patients with core-binding factor acute myeloid leukemia treated at our institution. Further research is necessary to determine the optimal monitoring strategies for these patients.