Successful mobilization of peripheral blood HPCs with G–CSF alone in patients failing to achieve sufficient numbers of CD34+ cells and/or CFU–GM with chemotherapy and G–CSF

BACKGROUND: Mobilization with chemotherapy and G–CSF may result in poor peripheral blood HPC collection, yielding <2 × 106 CD34+ cells per kg or <10 × 104 CFU–GM per kg in leukapheresis procedures. The best mobilization strategy for oncology patients remains unclear. STUDY DESIGN AND METHODS: In 27 patients who met either the CD34 (n = 3) or CFU–GM (n = 2) criteria or both (n = 22), the results obtained with two successive strategies—that is, chemotherapy and G–CSF at 10 μg per kg (Group 1, n = 7) and G–CSF at 10 μg per kg alone (Group 2, n = 20) used for a second mobilization course—were retrospectively analyzed. The patients had non-Hodgkin's lymphoma (5), Hodgkin's disease (3), multiple myeloma (5), chronic myeloid leukemia (1), acute myeloid leukemia (1), breast cancer (6), or other solid tumors (6). Previous therapy consisted of 10 (1-31) cycles of chemotherapy with additional chlorambucil (n = 3), interferon (n = 3), and radiotherapy (n = 7). RESULTS: The second collection was undertaken a median of 35 days after the first one. In Group 1, the results of the two mobilizations were identical. In Group 2, the number of CD34+ cells per kg per apheresis (0.17 [0.02-0.45] vs. 0.44 [0.11-0.45], p = 0.00002), as well as the number of CFU–GM (0.88 [0.00-13.37] vs. 4.19 [0.96-21.61], p = 0.00003), BFU–E (0.83 [0.00-12.72] vs. 8.81 [1.38-32.51], p = 0.00001), and CFU-MIX (0.10 [0.00-1.70] vs. 0.56 [0.00-2.64], p = 0.001134) were significantly higher in the second peripheral blood HPC collection. However, yields per apheresis during the second collection did not significantly differ in the two groups. Six patients in Group 1 and 18 in Group 2 underwent transplantation, and all but one achieved engraftment, with a median of 15 versus 12 days to 1,000 neutrophils (NS), 22 versus 16 days to 1 percent reticulocytes (NS), and 26 versus 26 days to 20,000 platelets (NS), respectively. However, platelet engraftment was particularly delayed in many patients. CONCLUSION: G–CSF at 10 μg per kg alone may constitute a valid alternative to chemotherapy and G–CSF to obtain adequate numbers of peripheral blood HPCs in patients who previously failed to achieve mobilization with chemotherapy and G–CSF. This strategy should be tested in prospective randomized trials.