Minimal Residual Disease in Acute Lymphoblastic Leukemia: Current Practice and Future Directions

Simple Summary

Acute lymphoblastic leukemia minimal residual disease (MRD) refers to the presence of residual leukemia cells following the achievement of complete remission, but below the limit of detection using conventional morphologic assessment. Up to two thirds of children may have MRD detectable after induction therapy depending on the biological subtype and method of detection. Patients with detectable MRD have an increased likelihood of relapse. A rapid reduction of MRD reveals leukemia sensitivity to therapy and under this premise, MRD has emerged as the strongest independent predictor of individual patient outcome and is crucial for risk stratification. However, it is a poor surrogate for treatment effect on long term outcome at the trial level, with impending need of randomized trials to prove efficacy of MRD-adapted interventions.

Abstract

Acute lymphoblastic leukemia (ALL) is the most common pediatric cancer and advances in its clinical and laboratory biology have grown exponentially over the last few decades. Treatment outcome has improved steadily with over 90% of patients surviving 5 years from initial diagnosis. This success can be attributed in part to the development of a risk stratification approach to identify those subsets of patients with an outstanding outcome that might qualify for a reduction in therapy associated with fewer short and long term side effects. Likewise, recognition of patients with an inferior prognosis allows for augmentation of therapy, which has been shown to improve outcome. Among the clinical and biological variables known to impact prognosis, the kinetics of the reduction in tumor burden during initial therapy has emerged as the most important prognostic variable. Specifically, various methods have been used to detect minimal residual disease (MRD) with flow cytometric and molecular detection of antigen receptor gene rearrangements being the most common. However, many questions remain as to the optimal timing of these assays, their sensitivity, integration with other variables and role in treatment allocation of various ALL subgroups. Importantly, the emergence of next generation sequencing assays is likely to broaden the use of these assays to track disease evolution. This review will discuss the biological basis for utilizing MRD in risk assessment, the technical approaches and limitations of MRD detection and its emerging applications.

Pediatric Acute Lymphoblastic Leukemia, Version 2.2020, NCCN Clinical Practice Guidelines in Oncology

Acute lymphoblastic leukemia (ALL) is the most common pediatric malignancy. Advancements in technology that enhance our understanding of the biology of the disease, risk-adapted therapy, and enhanced supportive care have contributed to improved survival rates. However, additional clinical management is needed to improve outcomes for patients classified as high risk at presentation (eg, T-ALL, infant ALL) and who experience relapse. The NCCN Clinical Practice Guidelines in Oncology (NCCN Guidelines) for pediatric ALL provide recommendations on the workup, diagnostic evaluation, and treatment of the disease, including guidance on supportive care, hematopoietic stem cell transplantation, and pharmacogenomics. This portion of the NCCN Guidelines focuses on the frontline and relapsed/refractory management of pediatric ALL.

Outcome and Clinical Significance of Immunophenotypic Markers Expressed in Different Treatment Protocols of Pediatric Patients With T-ALL in Developing Countries

BACKGROUND

T-cell acute lymphoblastic leukemia (T-ALL) accounts for about 15% of pediatric ALL. With wider use of intensive chemotherapy, the prognosis for childhood T-ALL has improved. Further gains in treatment outcome will likely require methods to identify patients who continue to fail on contemporary protocols. This study aimed to evaluate pediatric patients with T-ALL at 2 different Arabic cancer centers regarding their clinicopathologic, immunophenotypic, and cytogenetic features and outcome.

PATIENTS AND METHODS

This retrospective study included all children with T-ALL treated between 2003 and 2013 at 2 oncology centers in the Middle East. Patients were divided into (group I) treated with Berlin-Frankfurt-Münster (BFM)-90 treatment protocol between February 2003 and June 2007 and (group II) includes all patients treated thereafter by the Total Therapy Study XIII protocol for high-risk ALL.

RESULTS

This study included 103 patients with a median age of 8.9 years. The male to female ratio was 2.6:1. The median initial white blood cell count was 123 × 10⁹/L. Central nervous system leukemia was detected in 15%. The early T-cell precursor (ETP)-ALL phenotype was found in 16.5%. The 5-year overall survival was 20.7% ± 67.5% and 72.9% ± 5.7% (P < .01); the 5-year disease-free survival was 47.1% ± 13.8% and 77.3% ± 6.0% (P = .023); and the 5-year event-free survival was 28.6% ± 12.1% and 71.1% ± 6.2% (P = .003) for group I and II, respectively.

CONCLUSION

The outcome of patients with T-ALL significantly improved in patients who received the treatment protocol of ALL with high-risk criteria. This protocol eliminates the bad outcomes effect of several clinical and immunophenotypic markers. Patient with the ETP-ALL phenotype had a nonsignificant inferior outcome compared with the non-ETP-ALL group.