[en] BACKGROUND: Mobilization with chemotherapy and G-CSF may result in poor peripheral blood HPC collection, yielding <2 x 10(6) CD34+ cells per kg or <10 x 10(4) 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 microg per kg (Group 1, n = 7) and G-CSF at 10 microg 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 microg 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.