Comparison of salvage chemotherapy regimens and prognostic significance of minimal residual disease in relapsed/refractory acute myeloid leukemia
Muhammad Umair Mushtaq , Alexandra M. Harrington , Sibgha Gull Chaudhary , Laura C. Michaelis , Karen-Sue B. Carlson , Sameem Abedin , Lyndsey Runass , Natalie S. Callander , Michael J. Fallon , Mark Juckett , Aric C. Hall , Peiman Hematti , Ryan J. Mattison , Ehab L. Atallah & Guru Subramanian Guru Murthy
To cite this article: Muhammad Umair Mushtaq , Alexandra M. Harrington , Sibgha Gull Chaudhary , Laura C. Michaelis , Karen-Sue B. Carlson , Sameem Abedin , Lyndsey Runass , Natalie S. Callander , Michael J. Fallon , Mark Juckett , Aric C. Hall , Peiman Hematti , Ryan J. Mattison , Ehab L. Atallah & Guru Subramanian Guru Murthy (2020): Comparison of salvage chemotherapy regimens and prognostic significance of minimal residual disease in relapsed/ refractory acute myeloid leukemia, Leukemia & Lymphoma, DOI: 10.1080/10428194.2020.1821009
To link to this article: https://doi.org/10.1080/10428194.2020.1821009
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ImageImageLEUKEMIA & LYMPHOMA
https://doi.org/10.1080/10428194.2020.1821009
ORIGINAL ARTICLE
Comparison of salvage chemotherapy regimens and prognostic significance of minimal residual disease in relapsed/refractory acute myeloid leukemia
Muhammad Umair Mushtaqa,b Image, Alexandra M. Harringtonc, Sibgha Gull Chaudharya,b,
Laura C. Michaelisd, Karen-Sue B. Carlsond, Sameem Abedind, Lyndsey Runassd, Natalie S. Callandera,b, Michael J. Fallonb, Mark Jucketta,b, Aric C. Halla,b, Peiman Hemattia,b, Ryan J. Mattisona,b, Ehab L. Atallahd and Guru Subramanian Guru Murthyd
aDivision of Hematology/Oncology, Department of Medicine, University of Wisconsin School of Medicine and Public Health, Madison, WI, USA; bUniversity of Wisconsin Carbone Cancer Center, Madison, WI, USA; cDepartment of Pathology, Medical College of Wisconsin, Milwaukee, WI, USA; dDivision of Hematology/Oncology, Department of Medicine, Medical College of Wisconsin, Milwaukee, WI, USA
ABSTRACT
We compared the outcomes of salvage chemotherapy in 146 patients with relapsed (57.5%) or refractory (42.5%) AML who received CLAG-M (51%), MEC (39%) or CLAG (10%). Minimal residual disease (MRD) was assessed by flow cytometry. Bivariate, Kaplan–Meier, and Cox regression anal- yses were conducted. Complete remission (CR) rate of 46% (CLAG-M 54% versus MEC/CLAG 40%, p ¼ .045) was observed with MRD-negative CR of 33% (CLAG-M 39% versus MEC/CLAG
22%, p ¼ .042). Median overall survival (OS) was 9.7 months; the longest OS occurred with CLAG- M (13.3, 95%CI 2.4–24.3) versus MEC (6.9, 95%CI 2.9–10.9) or CLAG (6.2, 95%CI 2.4–12.6) (p ¼ .025). When adjusted for age, gender, relapsed/refractory AML, poor risk AML, MRD, chemo-
95% CI 0.07–0.30, p < .001) and transplant (HR 0.22, 95% CI 0.13–0.39, p < .001) were associated with higher OS. Our findings confirm that CLAG-M is a reasonable salvage regimen for RR-AML followed by transplant. therapy and transplant, CLAG-M (HR 0.63, 95% CI 0.40–0.98, p ¼ .042), MRD-negativity (HR 0.15,
ARTICLE HISTORY
Received 13 July 2020
Revised 19 August 2020
Accepted 22 August 2020
KEYWORDS
Acute myeloid leukemia; salvage chemotherapy; relapsed/refractory leuke- mia; hematopoietic stem cell transplant; minimal residual disease
Introduction
Acute myeloid leukemia (AML) is a hematologic malig- nancy evolving from clonal expansion of myeloid blasts and generally affects older adults [1]. Despite a complete remission (CR) rate of 60–80% with initial induction therapy, more than 50% of AML patients experience disease relapse [2]. The prognosis of patients with relapsed/refractory AML (RR-AML) is often poor and the response to salvage therapy is influenced by factors such as age, cytogenetics, prior stem cell transplantation, and duration of first CR [3,4]. Additionally, older age and chemotherapy resistance imposes significant challenges in achieving second CR in these patients.
Induction therapy for AML with a cytarabine-anthra- cycline regimen (7 þ 3) has been the standard for fit patients for more than 30 years; however, there is no standard salvage therapy for RR-AML. Several chemo- therapy regimens have been used for the treatment of patients with RR-AML, but the choice is often based upon individual clinical experience as there are limited prospective randomized trials. Although most of these regimens have chemotherapy agents with known anti- leukemia activity, including topoisomerase inhibitors (anthracyclines and etoposide) and antimetabolites (cytarabine, fludarabine, and cladribine), the response rates have varied between 40% and 50% [5]. While the response to therapy has been conventionally assessed using morphologic remission, there is emerg- ing data to support to use of minimal/measurable residual disease (MRD) testing, as deeper responses correlate with improved long-term outcomes [6–13]. In the current study, we examined the outcomes of patients with RR-AML who received three commonly used salvage regimens, cladribine, cytarabine, and fil- grastim with mitoxantrone (CLAG-M) or without mitox- antrone (CLAG), and mitoxantrone, etoposide, and
CONTACT Guru Subramanian Guru Murthy Image [email protected] ImageDivision of Hematology/Oncology, Department of Medicine, Medical College of Wisconsin, Milwaukee, 53226 WI, USA
Image Supplemental data for this article can be accessed here.
© 2020 Informa UK Limited, trading as Taylor & Francis Group
M. U. MUSHTAQ ET AL. cytarabine (MEC), and explored the impact of MRD status in this setting.
Methods
Design, setting, and patients We conducted a multicenter retrospective study, including RR-AML patients (n ¼ 146) who underwent
salvage therapy at the University of Wisconsin and Medical College of Wisconsin from 2009 to 2018. The study was approved by the institutional review boards at respective institutions. Inclusion criteria for the study were patients with age 18 years or above, diag- nosed with AML in disease relapse or refractory status, who received one of the three regimens: cladribine 5 mg/m2, cytarabine 2 g/m2, and filgrastim 300 mcg for 5 days without (CLAG) or with mitoxantrone 10 mg/m2 for 3 days (CLAG-M); or mitoxantrone 6 mg/m2, etopo- side 80 mg/m2 and cytarabine 1 g/m2 for 6 days (MEC), and were actively followed after treatment. Refractory AML was defined as the failure to achieve remission after one or more courses of induction chemotherapy. Relapsed AML was defined as evidence of relapsed disease after having achieved morphologic remission after induction chemotherapy. Acute promyelocytic leukemia (APML) patients were excluded. During sal- vage therapy, patients were admitted to the hospital for close monitoring and supportive care. Patients received prophylactic antimicrobials and transfusion support according to the standard institutional guide- lines. Bone marrow biopsies were obtained for response assessment after salvage therapy either at the recovery of blood counts or up to 42 days after therapy, whichever was earlier.
Data collection
Data were collected by medical record review. Demographic, clinical, and pathologic factors were ascertained at the time of RR-AML diagnosis. AML sub- groups were defined as per the World Health Organization (WHO) 2008 classification [14]. AML risk stratification was based on the European Leukemia Network (ELN) 2010 guidelines [15]. The risk stratifica- tion was based on cytogenetics, fluorescent-in-situ hybridization (FISH) for t(8;21), inv(16), inv(3), 11q23, del(5), and del(7) and available molecular data. NPM1 and FLT3 status were available for 119 patients. Treatment response after salvage therapy was assessed using the ELN 2010 guidelines response crite- ria [15]. CR was defined as bone marrow myeloblasts <5% with absolute peripheral blood neutrophil count ≥1000 cells/mL and platelet ≥100,000 cells/mL. CR without platelet recovery or neutrophil recovery was defined as CR with incomplete hematologic recovery (CRi). Minimal residual disease (MRD) was assessed at the Medical College of Wisconsin by 8-color flow
cytometry in patients who achieved CR or CRi. Briefly, EDTA-anticoagulated bone marrow aspirates were lysed, and cell suspensions were prepared for incuba- tion with 8 different fluorochrome-labeled antibodies per tube.
Antibodies analyzed across multiple tubes include: CD7, CD11b, CD13, CD14, CD15, CD22, CD33, CD34, CD36, CD38, CD45, CD56, CD64, CD117, and
HLA-DR. At least 200,000–500,000 events were col- lected per tube on a FACS CANTO cytometer (BD Biosciences, Franklin Lakes, NJ) and analyzed with Paint-A-Gate software (BD Biosciences, Franklin Lakes, NJ). Blasts were identified using cluster analysis, based on reproducible forward and light scatter properties and CD45 staining across tubes, along with the identi- fication of other cell populations. Aberrant blast immunophenotypes were identified based on com- parison with reproducible, known blast antigen expression patterns. Comparisons were also made to previous leukemic blast immunophenotypes when available. MRD was defined as at least a 0.01% popula- tion of aberrant myeloblasts in the absence of mor- phologic evidence of disease. MRD analysis was available for 126 patients, including all refractory (n ¼ 74) and 72% of the patients in CR (n ¼ 52/72).
Statistical analysis
Descriptive statistics were used to compare baseline demographic characteristics. Categorical variables were compared using the Chi-square test. Continuous variables were compared using ANOVA. Overall sur- vival (OS) was calculated from the time of diagnosis to death from any cause and patients were censored if they were alive at the last follow-up. Survival probabil- ities were computed using the Kaplan–Meier method and compared with the log-rank test. Cox regression analyses were used to determine significant factors that influence OS. Hazard ratios (HR) with 95% confi- dence intervals (CI) were obtained. Multivariate cox regression analyses, simultaneously adjusted for age, gender, relapsed versus refractory AML, poor risk AML, salvage chemotherapy regimen (CLAG-M versus others), MRD, subsequent allogeneic hematopoietic stem cell transplant (HSCT), and subsequent chemo- therapy, were conducted to quantify the independent predictors of OS. Statistical analysis was performed using SPSS version 21 (SPSS Inc, Chicago, IL). Statistical significance was considered at p < .05.
Results
Baseline characteristics
The study included 146 patients with relapsed (57.5%) or refractory (42.5%) AML who received CLAG-M (51%), MEC (39%) or CLAG (10%) salvage chemother- apy. Baseline characteristics were similar between the three groups (Table 1). The median age was 60 years (range 22–77) and 59% of patients were male. AML was classified as AML with recurrent genetic abnor- malities (23%), AML with myelodysplasia-related changes (25%), therapy-related AML (8%) and AML not otherwise specified (44%). AML risk status was good (16%), intermediate (32%) and poor (52%). Cytogenetics were good (5%), intermediate (59%) and poor (36%). Of the 119 patients with available molecu- lar data, NPM1 (17%), FLT3-ITD (16%), and FLT3-TKD
Discussion
Relapsed/refractory AML represents a challenging clin- ical situation. The introduction of novel agents such as venetoclax and targeted therapies for FLT3 and IDH mutations are increasing options for the management of RR-AML patients. Although there has been survival benefit with novel agents in RR-AML, prospective trials have shown CR rates of 19–22% with ivosidenib (IDH1 inhibitor), enasidenib (IDH2 inhibitor) and gilteritinib (FLT3 inhibitor) [16–18]. Most centers prefer intensive salvage regimens for fit patients as they may yield higher, faster response rates and enable them to undergo subsequent allogeneic stem cell transplant with curative intent. Unfortunately, prospective randomized trials of RR-AML have shown dismal results and experimental agents have failed to achieve better response rates or survival compared to standard chemotherapy agents [2,5,19–22]. In a phase II randomized study, CPX-351 demonstrated a CR rate of 37% compared to 32% with standard chemotherapy [23]. A phase II randomized trial reported an overall response of 28% with flavopiridol, cytarabine, and mitoxantrone (FLAM) and 16% with sirolimus-MEC (S-
MEC) [24].
A phase III randomized trial noted a CR rate of 25% with MEC and 17% with valspodar-MEC [25]. In patients fit for aggressive therapy, the NCCN guide- lines suggest the use of anthracycline (mitoxantrone or idarubicin) with high-dose cytarabine or cytarabine in combination with etoposide or purine analogs (cla- dribine, fludarabine or clofarabine) [26]. At present, there is limited randomized prospective literature to guide the choice of salvage chemotherapy and clinical practice is often based on retrospective analyses.
Earlier studies in the 1980s reported the efficacy of combination therapy with anthracyclines or etoposide with cytarabine in RR-AML [27,28]. Previous single-arm studies and retrospective series have shown widely disparate response rates with MEC from 18–66% [29–32]. Utilizing combinations of purine nucleoside analogs with cytarabine to increase the intracellular accumulation of cytotoxic Ara-C-5t triphosphate (ara- CTP) and addition of G-CSF to sensitize the leukemic cells to higher doses of cytarabine were innovations from the 1990s that led to the development of CLAG and FLAG regimens, utilizing cladribine or fludarabine with intermediate doses of cytarabine and G-CSF [33–35]. Single-arm studies of the combination of cytarabine and cladribine with or without mitoxan- trone/idarubicin [36–39], or fludarabine with or with- out idarubicin [40–46], or clofarabine [47], showed very promising activity with CR rates of 50–58%, 49–63%, and 46%, respectively.
A previous retrospective comparative study includ- ing 162 RR-AML patients has shown the superiority of CLAG (CR 38%, OS 7.3 months) over MEC (CR 24%, OS 4.5 months) [48]. A prospective cohort study demon- strated the superiority of CLAG over FLAG in 103 RR- AML patients with CR rates of 62% versus 49%, respectively [49]. A retrospective study with 56 RR- AML patients noted a higher CR (55%) with CLAG-M compared to CLAG (44%). Poor risk and refractory/sec- ondary AML were associated with worse outcomes [50]. A recent phase I/II study of CLAG with dose-esca- lated mitoxantrone to 18 mg/m2 noted impressive effi- cacy with 79% CR and 71% MRD-negative CR rates and a median OS of 33 months. Cytogenetic risk and secondary AML were associated with worse response rates [51].
While none of the currently used salvage chemo- therapy regimens have been compared head-to-head in prospective trials, to our knowledge, our study is the first large retrospective multicenter comparative analysis of the commonly used mitoxantrone-based salvage regimens and identifies the impact of MRD status in this setting. In our study, CLAG-M compared to MEC or CLAG lead to better OS in the multivariate analysis adjusted for common confounding factors, including age, gender, relapsed versus refractory AML, AML risk group, subsequent stem cell transplant, and subsequent chemotherapy.
Among patients who achieve morphologic remis- sion, subclinical residual leukemic cells referred to as “minimal or measurable residual disease” have higher chances of disease persistence and eventual relapse [8,9,52]. Post-therapy morphologic response and MRD have been shown to have independent prognostic sig- nificance [7,10,11], and the effect of pretreatment vari- ables like cytogenetics/molecular studies and relapsed or refractory AML was less marked once MRD is taken into consideration [7,11]. The negative impact of pre- transplant MRD determined by flow cytometry is simi-
lar for AML in first and second CR, with even minute detectable levels (≤0.1%) associated with adverse out- comes [6]. Pre-transplant MRD strongly predicts post- transplant outcomes and intensification of condition- ing therapy in MRD-positive AML patients undergoing HSCT results in improved survival [12,13].
We observed this effect clearly in our cohort with significantly better outcomes for patients with MRD-negative CR as com- pared to MRD-positive CR. CLAG-M produced more MRD negative CR as compared to the other regimens, which likely explains the survival advantage demon- strated in our analysis. In the adjusted multivariate analysis, only MRD-negative status, use of CLAG-M and stem cell transplant after salvage therapy independ- ently predicted better OS while relapsed versus refrac- tory disease and risk status did not have a significant association. Similar survival outcomes were observed in the subset of patients who had prior HSCT.
Our findings support the use of CLAG-M as a sal- vage chemotherapy backbone in patients with RR- AML and the role of post-therapy MRD assessment in this setting. Our data are limited by the retrospective nature of the study, highlighting the need for pro- spective randomized studies to validate the findings. We did not collect and report toxicity data due to unreliable reporting in retrospective chart review; however, overall survival statistics account for both relapse and non-relapse mortality. While we observed promising remission rates and survival in our study, there is still an unmet need in RR-AML patients. Further studies with investigational/novel agents in combination with chemotherapy followed by a stem cell transplant and/or cellular therapy will hopefully improve the outcomes in this therapeutically challeng- ing patient population.
Conclusion
CLAG-M compared to MEC or CLAG is associated with significantly better OS in RR-AML regardless of age, refractory versus relapsed AML, AML risk status, and subsequent chemotherapy and stem cell transplant. Patients treated with CLAG-M were more likely to achieve MRD-negativity. After adjusting for all factors, MRD-negative status, use of CLAG-M, and stem cell transplant after salvage therapy were independent predictors of better OS. Our findings confirm that CLAG-M is a reasonable salvage regimen for RR-AML, followed by allogeneic hematopoietic stem cell transplantation.
Disclosure statement
The authors report no conflict of interest. Ehab Atallah has a financial relationship (consultancy) with Novartis, BMS, Jazz, Abbvie, and Pfizer.
Funding
This work was supported by the University of Wisconsin Carbone Cancer Center Support Grant P30 CA014520.
ORCID
Muhammad Umair Mushtaq Image http://orcid.org/0000-0001- 8122-0563
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