[Prognostic significance of early assessment of minimal residual disease in acute myeloid leukemia with mutated NPM1 patients]

NPM1 Mutation Analysis in Acute Myeloid Leukemia: Comparison of Three Techniques - Sanger Sequencing, Pyrosequencing, and Real-Time Polymerase Chain Reaction

OBJECTIVE

Nucleophosmin-1 (NPM1) mutations have prognostic importance in acute myeloid leukemia (AML) patients with intermediate-risk karyotype at diagnosis. Approximately 30% of newly diagnosed cytogenetically normal AML (CN-AML) patients harbor the NPM1 mutation in India. In this study we compared the efficiency of three molecular techniques in detecting NPM1 mutation in peripheral blood and bone marrow samples.

MATERIALS AND METHODS

In a single-center cohort we analyzed 165 CN-AML bone marrow/peripheral blood samples for NPM1 mutation analysis. About 30% of the CN-AML samples revealed NPM1 mutations. For the detection, three methods were compared: Sanger sequencing, pyrosequencing, and real-time polymerase chain reaction (PCR).

RESULTS

NPM1 exon 12 mutations were observed in 52 (31.51%) of all CN-AML cases. The sensitivity of Sanger sequencing, pyrosequencing, and real-time PCR was 80%, 90%, and 95%, whereas specificity was 95%, 100%, and 100%, respectively. The minimum limit of mutation detection was 20%-30% for Sanger sequencing, 1%-5% for pyrosequencing, and 0.1%-1% for real-time PCR.

CONCLUSION

The sequencing method, which is the reference method, has the lowest sensitivity and is sometimes difficult to interpret. Real-time PCR is a highly sensitive method for mutation detection but is limited for specific mutation types. In our study, pyrosequencing emerged as the most suitable technique for the detection of NPM1 mutations on the basis of its easy interpretation and less time-consuming processes than Sanger sequencing.

[Minimal residual disease level predicts outcomes in the non-favorable risk patients with acute myeloid leukemia]

Objective: To explore impact of minimal residual leukemia (MRD) on outcomes in the non-favorable risk adults with de novo acute myeloid leukemia (AML) . Methods: From January 2008 to February 2016, data of consecutive newly-diagnosed non-favorable risk adults with AML (non-APL) according to SWOG criteria who achieved morphologic leukemia-free state (MLFS) and received continuous chemotherapy were assessed retrospectively. Results: 292 AML patients were enrolled, 150 (51.4%) were male. Median age was 46 years (range, 18-65 years) . Using the SWOG cytogenetic classification, 186 (63.7%) , 49 (16.8%) and 57 (19.5%) patients belonged to intermediate, unfavorable and unknown categories, respectively. With a median follow-up period of 15 months (range, 1 to 94 months) in survivors, the probabilities of cumulative rates of relapse (CIR) , disease free survival (DFS) and overall survival (OS) at 2-years were 51.6%, 42.6% and 60.0%, respectively. Multivariate analyses showed that MRD positive (defined as Q-PCR WT1 mRNA ≥0.6% or any level of abnormal blast population detected by flow cytometry) after achieving MLFS and PLT<100×10(9)/L were common adverse factors affecting CIR and DFS. In addition, positive FLT3-ITD mutation and CRp/CRi had negatively impact on CIR, DFS and OS. Monosomal karyotype was adverse factors affecting CIR and OS. Age ≥44 years and unfavorable-risk of SWOG criteria were associated with shorter DFS. Conclusions: MRD level after achieving MLFS had prognostic significance on outcomes in non-favorable adults with AML who received continuous chemotherapy after achieving MLFS.