The impact of recent vincristine on human hematopoietic progenitor cell collection in pediatric patients with central nervous system tumors

Background Central nervous system (CNS) malignancies represent 20% of all childhood cancers. To improve outcomes in infants and children with high-risk disease, treatment can include adjuvant chemotherapy and early autologous peripheral blood human progenitor cell collection (AHPCC), followed by high-dose chemotherapy and stem cell rescue. In many protocols, postoperative chemotherapy includes the administration of weekly vincristine (VCR) between induction chemotherapy cycles, regardless of scheduled AHPCC. We observed anecdotal AHPCC failures in children receiving midcycle VCR (MC-VCR). Study Design and Methods The study was an 8-year retrospective chart review of all children with a CNS malignancy and who underwent AHPCC. Information included patient demographic and clinical data, mobilization regimen, VCR administration, product yields, infusion toxicity, and patient charges. Data were analyzed relative to MC-VCR administration. Graphics and statistical analysis (t-test, chi-square, linear regression) were performed with commercial software. Results Twenty-four patients and 47 AHPCCs were available for analysis. Nine patients (37%) received MC-VCR within 7 days of scheduled AHPCC. MC-VCR was associated with delayed marrow recovery (17.9 days vs. 14.9 days, p = 0.0012), decreased median peripheral CD34 counts (75 × 10⁶ CD34/L vs. 352 × 10⁶ CD34/L, p = 0.03), decreased median CD34 yields (2.4 × 10⁶ CD34/L vs. 17.8 × 10⁶ CD34/kg, p = 0.08), more AHPCCs per mobilization (2.9 vs. 1.1, p = 0.01), and an increased rate of remobilization (33% vs. 6%). Mean patient charges were 2.5× higher in patients receiving MC-VCR than controls (p = 0.01). Conclusion MC-VCR should be withheld before scheduled AHPCC to optimize CD34 collection.