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Background A proportion of candidates for high-dose chemotherapy with autologous PBPC support (HDC-PBPCS) will not provide an adequate PBPC yield from their first mobilization. The value of re-mobilization and the best regimen for re-mobilization in these patients is unclear. Methods: In 23 patients who failed to provide ≥ 3 × 10[sup 6] CD34[sup +] cells/kg after their first mobilization, PBPC were re-mobilized using a regimen of simultaneous administration of G-CSF and GM-CSF (10 μg/kg/day each) with leukaphereses (LP) starting Day 4 or 5 of CSF administration. Yields of WBC/kg, MNC/kg and CD34[sup +] cells/kg/L of processed blood total CD34[sup +] were compared between the first and second mobilization in each patient. The ability of the combined yield from the two mobilizations to achieve the desired threshold PBPC yield and the tolerability of the re-mobilization were determined. Results: The re-mobilization regimen was well-tolerated and no patient discontinued the regimen because of toxicity. Median collected WBC/kg/L (1.37 × 10[sup 7] versus 2.62 × 10[sup 7], p = 0.0065), MNC/kg/L (0.77 × 10[sup 7] versus 1.97 × 10[sup 7], p = 0.0003), CD34[sup +]cells/kg/L (1.64 × 10[sup 7] versus 4.18 × 10[sup 7], p = 0.001) were significantly higher after the second mobilization (G-CSF/GM-CSF combination). Percentage of CD34[sup +] cells in the leukapheresis was also significantly higher after the second mobilization (median 0.104% versus 0.195%, p = 0.036). Twelve of 22 patients achieved the target PBPC dose (> 3 × 10[sup 6]/CD34[sup +] cells/kg) after two mobilizations (six patients achieved the target from the second mobilization alone). A further eight underwent HDC-PBPCS without achieving the target PBPC dose. These patients experienced a significant delay in neutrophil and platelet engraftment when compared with those patients achieving the target dose. Discussion: This study demonstrates that the combination of G-CSF and GM-CSF is an effective and tolerable method for re-mobilization of PBPC in patients who fail to provide an adequate yield from their first mobilization. [ABSTRACT FROM AUTHOR]