A mononuclear cell dose of 3 x 10⁵/kg predicts early multilineage recovery in patients with malignant lymphoma treated with carmustine, etoposide, Ara-C and melphalan (BEAM) and peripheral blood progenitor cell transplantation

We have assessed the potential use of the mononuclear cell (MNC) content as the sole assessment of graft quality in 35 patients receiving BEAM (carmustine, etoposide, cytosine arabinoside, melphalan) chemotherapy and autologous peripheral blood progenitor cell (PBPC) transplantation for malignant lymphoma. PBPCs were mobilized with cyclophosphamide and granulocyte colony-stimulating factor (G-CSF), and each patient underwent two (n = 20) or three (n = 15) apheresis procedures. Median cell yields were 5.03 x 10⁸ MNC/kg (range 1.59-15.70 x 10⁸) and 73.10 x 10⁴ CFU-GM/kg (range 0.09-346.72 x 10⁴). All patients achieved hematologic recovery. Median days to neutrophils ≥ 0.1 x 10⁹/L, neutrophils ≥ 0.5 x 10⁹/L, and platelets ≥ 25 x 10⁹/L were 11 (range 8-15), 13 (range 10-37), and 11 (range 7-41), respectively. A close correlation was observed between the MNC and CFU-GM dose (r = 0.79, p < 0.0001). We have previously defined a minimum threshold CFU-GM dose of 20 x 10⁴/kg for patients undergoing high-dose therapy. This corresponds with an MNC dose of 3 x 10⁸/kg. Comparison of engraftment in patients receiving 3 x 10⁸ MNC/kg with those receiving lower doses demonstrated significantly longer times to recovery of neutrophils to ≥ 0.5 x 10⁹/L and platelets to ≥ 25 x 10⁹/L. All patients receiving an MNC dose of ≥ 3 x 10⁸/kg achieved neutrophil and platelet recovery by days 12 and 24, respectively. These preliminary data demonstrate that for patients with lymphoma undergoing PBPC mobilization according to this protocol and treated with BEAM chemotherapy, assessment of MNC dose alone is sufficient to predict early hematologic recovery. Additional assays such as CFU-GM or CD34⁺ cell counts may not be necessary if this MNC dose is reinfused.