Transplanted CD34 ⁺ Cell Dose Is Associated with Long-Term Platelet Count Recovery following Autologous Peripheral Blood Stem Cell Transplant in Patients with Non-Hodgkin Lymphoma or Multiple Myeloma

Autologous hematopoietic stem cell transplantation (ASCT) is an established treatment for patients with hematologic malignancies, yet the impact of transplanted CD34 ⁺ cell dose on clinical outcomes is unresolved. We conducted post hoc analyses of transplanted CD34 ⁺ cell dose and hematopoietic recovery following ASCT in 438 patients with non-Hodgkin lymphoma (NHL) or multiple myeloma (MM), using data from 2 multicenter phase 3 clinical studies that compared plerixafor plus granulocyte-colony stimulating factor (G-CSF) versus placebo plus G-CSF as stem cell mobilization regimens. Days to engraftment and the proportion of patients who reached predetermined blood count thresholds were compared across 3 CD34 ⁺ cell dose levels: 2-4 × 10 ⁶ cells/kg, 4-6 × 10 ⁶ cells/kg, and >6 × 10 ⁶ cells/kg, regardless of mobilization treatment. Short-term neutrophil and platelet engraftment times were similar regardless of cell dose. A significant linear trend was observed between transplanted CD34 ⁺ cell dose and the proportion of patients with platelet count >150 × 10 ⁹/L at 100 days (P < .001), 6 months (P = 026), and 12 months (P = 020) in patients with NHL, and at 100 days in patients with MM (P = 004). A linear trend was also observed between transplanted cell dose and the proportion of patients with platelet count >100 × 10 ⁹/L at 100 days (P < .001) and 6 months (P = 023) in patients with NHL. A higher cell dose was associated with a lower percentage of NHL patients requiring red blood cell transfusions (P = 006). Our analyses confirm previous findings that transplanted CD34 ⁺ cell dose may be associated with better long-term platelet recovery after ASCT.