Comments by Prof. Jiajun Liu: Clinical impact of NPM1 mutation after chemotherapy in acute myeloid leukemia

Acute myeloid leukemia (AML) with mutations in the NPM1 gene (NPM1mut) is the most common recurrent genetically abnormal subtype of AML
.

Monitoring NPM1mut minimal residual disease (MRD) has an important role in patient evaluation after intensive chemotherapy
.

Approximately 25%-50% of NPM1mut patients have persistent MRD at the end of treatment (EOT) with a high risk of recurrence
.

The European Leukemia Network (ELN) defines molecular persistence of low copy number (MP-LCN) as MRD-positive complete remission (CR) with <1000 to 2000 transcripts per 105 ABL copies, collected after EOT The relative increase between 2 positive samples was <1-log
.

The UK National Cancer Institute task force reports the effect of pretransplant NPM1mut MRD on the risk of recurrence after allogeneic hematopoietic stem cell transplantation (HSCT)
.

However, the clinical prognosis of patients with persistent NPM1mut who did not receive transplantation is unclear
.

Therefore, this study sought to characterize the clinical impact of NPM1mut MRD in patients with EOT and to identify factors associated with disease progression
.

[1] Study methods Inclusion criteria: newly diagnosed NPM1mut AML patients received ≥2 cycles of intensive chemotherapy, NPM1mut MRD was present in the bone marrow at EOT, and patients were not scheduled to undergo HSCT at their first CR
.

UK patients were drawn from two UK National Cancer Institute prospective studies (AML17 study 2009-2014 and AML19 study June 2017-2019), and Australian patients were retrospectively identified in this study (2015-2020).
)
.

Bone marrow specimens were analyzed by quantitative reverse transcription polymerase chain reaction
.

Definitions of molecular progression or relapse (collectively referred to as molecular exhaustion), MP-LCN, and complete molecular remission (CRMRD-) were used with ELN MRD recommendations
.

Two subjects did not meet strict ELN criteria for molecular exhaustion: one did not increase molecular progression by 1-log10, and the other had molecular relapse in the absence of a definitive sample
.

Survival was assessed from EOT to death (overall survival [OS]) and/or morphological relapse (relapse-free survival [RFS]), and/or molecular failure (event-free survival [EFS])
.

Cox models were used for univariate and multivariate analysis
.

RESULTS: A total of 100 patients with NPM1mut MRD were included in the study, and the median time to last chemotherapy was 36 days (range 19-90 days)
.

The median age was 50 years, 85% of patients had a normal karyotype, and 39% had FLT3-internal tandem duplication (ITD) at diagnosis (17% allele ratio ≥0.
5)
.

At EOT, the median NPM1mut level was 13 copies (range 0.
3-20756; 5 patients >2000), with a median reduction from baseline of 4.
5-log (range 1.
8-6.
0; 7 patients had missing baseline data) )
.

In this cohort, patients' MRD levels at EOT were comparable regardless of the number of chemotherapy regimens completed (range, 2-5)
.

Patients with longer EOT MRD assessment time also had longer EFS and RFS
.

During a median follow-up of 23.
5 months, 29 patients died, of which 2 died after intensive rescue treatment
.

A total of 41 patients had morphological recurrence, 16 of whom had no prior molecular failure: 8 had MRD testing within 90 days of relapse (range 6-73 days) and 3 had testing >90 days later; 1 patient Extramedullary disease progression; 1 NPM1 wild-type relapse; 3 of these were unmonitored
.

Subsequent MRD levels met MP-LCN criteria in 39 patients (40%), and the 2-year EFS rate was 58%
.

To investigate the clinical impact of persistent NPM1mut MRD detected at EOT, patients' condition was assessed every 3 months
.

By the first analysis at 3 months, 9% of patients experienced morphological recurrence, 27% developed molecular failure, and 15% spontaneously acquired persistent CRMRD-
.

By 12-month analysis, 15% had morphological recurrence, 43% had molecular failure, 30% had CRMRD-, and 12% had MP-LCN (Figure 1)
.

At last follow-up, 9 patients (9%) had a median duration of MP-LCN of 14 months (range, 9-32 months) and a median survival of 20.
5 months (range, 9-35 months) )
.

From the start of the study, 31 patients (32%) spontaneously achieved CRMRD- for a duration of >6 months, and most patients (81%) achieved CRMRD- within the first 6 months, with only 1 patient subsequently progressing during follow-up
.

MP-LCN is a characteristic phenomenon in core-binding factor-AML (CBF-AML)
.

NPM1mut transcription persisted at >1000-2000 copies per 105 ABLs and was associated with a higher risk of disease recurrence
.

But in this study, that copy number could not be confirmed because the patient had received preemptive therapy before reaching that copy number
.

In addition, all 10 patients with molecular failure (>1-log increase) who did not receive preemptive therapy relapsed
.

At the last follow-up, the highest NPM1mut MRD level recorded in the 39 patients with event-free survival was only 90 copies
.

Paired peripheral blood and bone marrow sampling was not performed in this study
.

Therefore, the clinical relevance of MP-LCN in peripheral blood cannot be resolved
.

Of the 43 patients (44%) who experienced molecular failure within the preceding 12 months, 33 (77%) received preemptive salvage therapy prior to morphological recurrence, with significantly greater RFS compared with patients who did not receive preemptive salvage therapy prolongation (median 10.
6 vs 0.
7 months)
.

Time from EOT to molecular failure was similar in patients with and without preemptive therapy (median 64 vs 99 days)
.

Median time to start preemptive therapy after molecular failure was 27 days (range, 9-149 days), and treatment included FLAG-based (fludarabine + cytarabine + recombinant human granulocyte-stimulating factor) chemotherapy regimens (n=13 ), veneclax plus low-dose cytarabine (n=11), immediate HSCT (n=5), or others
.

In 10 patients who did not start salvage therapy until morphological relapse, the median interval between molecular failure and morphological relapse was 21 days (range 11-89 days)
.

Various MRD-guided preemptive therapies were used, ranging from azacitidine to intensive salvage chemotherapy; veneclax-based low-intensity therapy was previously reported to eliminate NPM1mut MRD in 11/12 (92%) patients.
role of hope
.

The survival benefit of preemptive therapy requires future prospective evaluation
.

The study also analyzed variables associated with molecular exhaustion, morphological recurrence, and death
.

In univariate analysis, variables significantly associated with molecular exhaustion were: white blood cell count and FLT3-ITD at diagnosis, chemotherapy courses received, and EOT NPM1mut MRD levels
.

In multivariate analysis (and confirmed by adverse selection), molecular exhaustion was only significantly associated with a reduction in baseline FLT3-ITD and EOT NPM1mut
.

Most patients (16%) with both baseline FLT3-ITD and EOT NPM1mut reduction risk factors relapsed within 4 months (median 1.
4 months), and few patients survived beyond 12 months (median 7.
3 months) )
.

Patients with 0 or 1 risk factor had 1-year EFS rates of 42% to 60% and 1-year OS rates of 80% to 88% (figure below)
.

The prognostic value of NPM1mut MRD after induction chemotherapy was previously reported, and the 3-year recurrence risk was 82% and 66% in patients with MRD still detectable in peripheral blood after 2 induction cycles or a <4-log reduction after induction
.

In a subgroup analysis of the UK cohort, these two adverse factors remained significant except for peripheral blood MRD status after cycle 2
.

A sensitivity analysis showed UK vs Australian cohorts (median 4.
6 vs 4.
4 log), standard vs high-dose cytarabine induction (4.
5 vs 4.
8-log), and with or without gemtuzumab (4.
8-log) vs 4.
5 log) with a similar magnitude of log reduction in MRD at EOT
.

Among patients diagnosed as FLT3-ITD-positive, a trend toward greater reduction in MRD at EOT was observed in patients treated with midostaurin (5.
1 vs 4.
4 log, p=0.
18), but switched to CRMRD during maintenance - No difference (36% vs 35%)
.

Conclusions NPM1mut MRD-positive patients who completed intensive chemotherapy and did not receive HSCT at the time of first remission had a substantial portion (42%) of their disease course that remained relapse-free within 1 year, or spontaneously achieved CRMRD- (30%), or was retained at low levels in bone marrow for 12 months (12%)
.

Risk factors associated with subsequent disease progression included concurrent FLT3-ITD at diagnosis and poor MRD response at EOT
.

This information is valuable for clinicians to use NPM1mut MRD for EOT transplantation decisions
.

The role of preemptive therapy in the management of molecular failure remains to be determined
.

Professor Liu Jiajun commented that many factors jointly affect the prognosis of AML, such as age, peripheral blood white blood cell count, cytogenetic abnormalities, MRD,
etc.

With the development of medical level and the emergence of various new drugs, the complete remission rate of leukemia has been greatly improved, but there are still a considerable number of patients who relapse after CR, shortening the survival period, and eventually leading to death.
Persistence of MRD in the bone marrow
.

MRD refers to the state in which a small number of leukemia cells remain in the body after a complete remission of leukemia induction chemotherapy (or after bone marrow transplantation).

.

MRD can be used as a sensitive indicator for prognostic evaluation
.

MRD <10-4 is less likely to recur, and MRD>10-4 indicates a high probability of disease recurrence, and the smaller the MRD value, the longer the recurrence-free survival (RFS)
.

In adult AML with normal karyotype, NPM1mut rates are 45% to 64%, more common in females, and it is one of the most common reproducible genetic abnormalities in the AML species
.

AML patients with NPM1mut without FLT3-ITD or with low-frequency FLT3-ITD mutation often have a good prognosis and are classified as low-risk group.
The guidelines point out that NPM1mut AML and FLT3-ITD low allele ratio may have a better prognosis, and patients are not Allogeneic hematopoietic cell transplantation should be performed routinely [2]
.

In the SWOG trial, patients aged 55-65 years with the NPM1-positive/FLT3-ITD-negative genotype had significantly improved 2-year overall survival (OS) relative to those without the subgenotype (70% vs 32%) ; P < 0.
001)
.

In addition, patients aged 55-65 years with the NPM1-positive/FLT3-ITD-negative genotype also had significantly improved 2-year OS compared with patients >65 years old with this genotype (70% vs 27%; P < 0.
001 ); patients > 65 years old with this genotype had a smaller potential survival benefit (27% vs 16%; P = 0.
33) [3]
.

However, if NPM1 is combined with FLT3-ITD high-frequency mutation, it still indicates a poor prognosis
.

Therefore, monitoring NPM1mut MRD has an important role in patient evaluation after intensive chemotherapy
.

A total of 100 patients with NPM1mut MRD were included in this study.
The study sought to characterize the clinical impact of NPM1mut MRD in patients with EOT and to identify factors associated with disease progression.
Patients were assessed every 3 months
.

Risk factors associated with subsequent disease progression include concurrent FLT3-ITD at diagnosis and poor MRD response at EOT
.

The results of this study enrich clinicians' prognostic judgments for AML patients and confirm that this information is valuable for clinicians to use NPM1mut MRD for EOT transplantation decisions
.

The general clinical conditions of patients, disease types, cytogenetic factors, grouping biological factors, and multi-drug resistance factors will all have different clinical effects on AML patients, and the specific effects of different factors at different stages of AML disease development are also affected.
Not all the same
.

Recent studies have shown that the persistent presence of NPM1mut in peripheral blood monitoring after two courses of induction chemotherapy is associated with the risk of relapse.
Is NPM1mut MRD status also an important factor in relapsed patients? In the future, randomized clinical studies with large samples are still needed to enrich the influence of NPM1mut MRD status and other factors on AML patients, and to enrich the clinical treatment and decision-making of AML
.

At present, there is no treatment method targeting NPM1mut or downstream signaling pathways for the treatment of patients with NPM1mut.
Recent clinical research results have identified a drug combination that is particularly effective for NPM1mut AML
.

Patients with NPM1mut have better curative effect after azacitidine + veneclax treatment.
In the subgroup analysis in Viale's study, 37 patients with NPM1mut were included, and the composite response rate of veneclase combined with azacitidine treatment is 66.
7%[4]
.

Another retrospective cohort study from MD Anderson Cancer Center included 303 patients with NPM1mut who received first-line AML therapy.
The composite response rate of veneclax + demethylating agent (HMA) treatment can be as high as 96%, which is comparable to that of NPM1mut.
Strong induction chemotherapy was similar, and the median OS was still not reached in the veneclax + HMA treatment group at 3.
7 years [5]
.

In addition, a single-center, single-arm, open-label phase II trial study was designed to evaluate the safety and efficacy of single-agent actinomycin in adult patients with relapsed/refractory (R/R) NPM1mut AML
.

Study results showed that after treatment, 4 patients achieved CR/CRi after one or two induction cycles, 3 patients who achieved CR relapsed within 7 months, but 1 patient received haploidentical hematopoietic stem cell transplantation , survived 4.
7 years after transplantation and had no MRD detected by RT-qPCR
.

The findings also show that actinomycin is a potential treatment option for relapsed/refractory NPM1mut AML
.

[6] Professor Liu Jiajun, chief physician, doctoral supervisor, director of the Department of Hematology, The Third Affiliated Hospital of Sun Yat-sen University, member of the Anti-Cancer Branch of the European Oncology Association, member of the Chinese Association for Immunology Apoptosis signal transduction mechanism, hematopoietic stem cell transplantation, molecular targeted therapy of hematological tumors, gene therapy and mechanism research of new anti-tumor drugs,
etc.

Medical expertise: more than 20 years in the clinical work of internal medicine hematology
.

For many years, he has been engaged in the research of leukemia cell apoptosis signal transduction mechanism and molecular targeted therapy of hematological tumors
.

Skilled in diagnosis and treatment of various anemia, bleeding disorders and hematological tumors
.

Diagnosis and treatment of diseases include hematopoietic stem cell transplantation for hematological diseases, leukemia chemotherapy, individualized treatment options for malignant hematological diseases such as malignant lymphoma and multiple myeloma, various unexplained anemias, unexplained long-term fever and differential diagnosis of lymphadenopathy and treatment,
etc.

References: [1] Ing S.
Tiong, Richard Dillon, Adam Ivey, et al.
Clinical impact of NPM1-mutant molecular persistence after chemotherapy for acute myeloid leukemia.
Blood Adv 2021;5(23):5107–5111.
doi: https://doi.
org/10.
1182/bloodadvances.
2021005455.
[2]DUPLOYEZ N, WILLEKENS C, MARCEAU-RENAUT A, et al.
2015.
Prognosis and monitoring of core-binding factor acute myeloid leukemia: current and emerging factors.
Expert Rev Hematol [J], 8: 43-56.
[3] Prognostic Significance of NPM1 Mutations in the Absence of FLT3–Internal Tandem Duplication in Older Patients With Acute Myeloid Leukemia: A SWOG and UK National Cancer Research Institute/Medical Research Council Report.
JCO.
2015.
2[4]DiNardo CD, et al.
N Engl J Med.
2020;383(7):617-629.
[5]Lachowiez CA, et al.
Blood Adv.
2020;4(7):1311-1320[6] Dactinomycin induces complete remission associated with nucleolar stress response in relapsed/refractory NPM1-mutated AML poke "read the original text", we progress together