Significance of minimal residual disease in pediatric mixed phenotype acute leukemia: a multicenter cohort study
Matthew J Oberley1,2, Sunil S Raikar3, Gerald B Wertheim4
1Department of Pathology and Laboratory Medicine, Children's Hospital Los Angeles, Los Angeles, CA, USA.
Abstract:
The rarity of mixed phenotype acute leukemia (MPAL) has precluded adequate data to incorporate minimal residual disease (MRD) monitoring into therapy. Fluidity in MPAL classification systems further complicates understanding its biology and outcomes; this includes uncertainty surrounding the impact of shifting diagnostic requirements even between iterations of the World Health Organization (WHO) classification. Our primary objective was to address these knowledge gaps. To do so, we analyzed clinicopathologic features, therapy, MRD, and survival in a centrally-reviewed, multicenter cohort of MPAL uniformly diagnosed by the WHO classification and treated with acute lymphoblastic leukemia (ALL) regimens. ALL induction therapy achieved an EOI MRD negative (<0.01%) remission in most patients (70%). EOI MRD positivity was predictive of 5-year EFS (HR = 6.00, p < 0.001) and OS (HR = 9.57, p = 0.003). Patients who cleared MRD by EOC had worse survival compared with those EOI MRD negative. In contrast to adults with MPAL, ALL therapy without transplantation was adequate to treat most pediatric patients. Earlier MRD clearance was associated with better treatment success and survival. Prospective trials are now necessary to validate and refine MRD thresholds within the pediatric MPAL population and to identify salvage strategies for those with poor predicted survival.
Insights
Minimal residual disease (MRD) monitoring is crucial in mixed phenotype acute leukemia (MPAL). Achieving MRD negativity early in treatment predicts better outcomes for pediatric MPAL patients, guiding future therapy.
Area of Science:
- Hematology
- Oncology
- Pediatric Hematology-Oncology
Background:
- Mixed phenotype acute leukemia (MPAL) is rare, limiting data for minimal residual disease (MRD) monitoring in treatment protocols.
- Evolving MPAL classification systems, including World Health Organization (WHO) guidelines, create uncertainty in understanding disease biology and patient outcomes.
- Standardizing MPAL diagnosis and treatment response assessment is essential for improving patient survival.
Purpose of the Study:
- To investigate the role of MRD monitoring in MPAL prognosis and treatment efficacy.
- To analyze clinicopathologic features, therapy, MRD status, and survival in a uniformly diagnosed MPAL cohort.
- To compare treatment outcomes between pediatric and adult MPAL patients treated with acute lymphoblastic leukemia (ALL) regimens.
Main Methods:
- Analysis of a multicenter cohort of MPAL patients uniformly diagnosed using WHO classification.
- Centralized review of clinicopathologic data, treatment regimens (ALL-based), and MRD levels at end of induction (EOI) and end of consolidation (EOC).
- Statistical analysis of MRD status, event-free survival (EFS), and overall survival (OS) using hazard ratios (HR) and p-values.
Main Results:
- Seventy percent of MPAL patients achieved EOI MRD negativity (<0.01%) with ALL induction therapy.
- EOI MRD positivity significantly predicted poorer 5-year EFS (HR=6.00, p<0.001) and OS (HR=9.57, p=0.003).
- Patients achieving MRD negativity by EOI had better survival than those with EOI MRD positivity; clearing MRD by EOC correlated with worse survival compared to EOI MRD negativity.
Conclusions:
- Early MRD negativity is a strong predictor of favorable outcomes in MPAL.
- ALL-based therapy is adequate for most pediatric MPAL patients, unlike adults who may require different strategies.
- Prospective trials are needed to establish validated MRD thresholds and optimal salvage strategies for pediatric MPAL.
