Comparison of the cellularity and presence of residual leukemia in bone marrow aspirate and biopsy specimens in pediatric patients with acute lymphoblastic leukemia (ALL) at day 7-14 of chemotherapy.

Background: Many pediatric chemotherapy protocols for treatment of ALL require a bone marrow examination at day 7 or day 14 after initiation of therapy. The usefulness of a bone marrow biopsy, in addition to an aspirate, has been a frequently asked question.
Procedure: This study addresses the evaluation of bone marrow cellularity and presence of residual leukemia in both aspirate and biopsy specimens in 45 consecutive pediatric patients (ages 1-19 years, 19 females, and 26 males) with ALL 7-14 days after initiation of therapy.
Discussion: 20/45 patients showed evidence of residual leukemia by bone marrow biopsy; 16/20 (80%) of these had evidence of residual leukemia in the aspirate specimen. Of the 4 aspirate specimens that did not demonstrate residual leukemia, 2 had <5% blasts and 2 had too few cells in the aspirate for evaluation. Of the 25/45 bone marrow biopsy specimens with no detectable residual leukemia, 14 of the aspirates had <5% blasts, and 11 had too few cells in the aspirate for evaluation. 13/45 (29%) of the aspirates had too few cells for a differential count. The bone marrow cellularity judged from the aspirate specimen was considered to be low (0-1+) in 34/45 patients. Of these 34 patients, the bone marrow biopsy showed hypocellularity (<20% cellularity) in 12/34, moderate cellularity (20-79% cellularity) in 14/34, and hypercellularity (>79% cellularity) in 8/34.
Conclusions: We conclude that both the bone marrow aspirate and biopsy specimens provide important information in evaluating the response to chemotherapy in pediatric patients with ALL at day 7-14 of induction chemotherapy. The aspirate alone may be misleading in terms of cellularity in many patients and may not provide evidence of residual leukemia.