Higher baseline natural killer cell counts are associated with a lower 8-day blast count and lower day 33 minimal residual disease in children with pediatric B-acute lymphoblastic leukemia.

Introduction: Acute lymphoblastic leukemia (ALL) is the most common malignancy in children. Despite advancements in treatment, a significant proportion of children relapse. Recently, immunotherapy has gained momentum and is becoming popular, especially for relapsed and refractory cases. NK cells are an important part of tumor immunity and are involved in the direct killing of tumor cells. Their role in B-ALL has not been explored. Therefore, this study was conducted to correlate the number of NK cells with standard prognostic parameters in B-ALL.

Methods: 25 subjects with newly diagnosed B-ALL between 0-14 years were recruited for the study from Pediatric OPD or emergency of the hospital. Along with a complete hemogram and peripheral smear examination, immunophenotyping by flow cytometry was done at the time of diagnosis for NK cell enumeration. The number of NK cells was correlated with standard prognostic parameters using the spearman correlation coefficient.

Results: Baseline NK cell percentage demonstrated a significant negative correlation with Prednisone poor day 8 blast response (P value = 0.02, r value = -0.44) and positive MRD (P value = 0.01, r value = -0.49) at day 33. A negative correlation was also noticed between NK cell percentage and unfavorable cytogenetics (hypodiploidy), although it was not significant (P value = 0.06, r value = -0.38). The number of NK cells did not correlate with age, gender and WBC count. Therefore, evaluating NK cells at diagnosis may serve as a simple and useful parameter for prognostication and risk stratification.

Conclusion: It may be assumed that a higher percentage of NK cells is associated with improved outcomes and probably a better prognosis. NK numbers may serve as an early independent parameter predicting prognosis and survival in children with B-ALL, thus helping to decide individual therapeutic regimens.