Effects of short-term in vivo administration of G-CSF on bone marrow prior to harvesting

The brief administration of G-CSF to previously treated solid tumor patients has a positive impact on the overall cellularity and progenitor cell content of harvested bone marrow. Fifty-seven patients, fully recovered from therapy and growth factor support, had approximately 500 mL of steady-state marrow harvested as outpatients under local anesthesia. Each patient then received 5 micrograms/kg of G-CSF every 12 hours subcutaneously for either 24 hours (21 patients), 36 hours (20 patients), or 48 hours (16 patients) just before harvesting 500 mL of activated bone marrow. Bone marrow cellularity (x 10(6)/mL) increased from a steady-state mean of 10.7 (+/- 0.9) to 25.7 (+/- 2.8) after 24 hours, 9.3 (+/- 0.7) to 29 (+/- 2.5) after 36 hours, and 9.6 (+/- 0.7) to 28.4 (+/- 2.5) after 48 hours. Although the percentage of CD34+ cells did not significantly change in stimulated marrow, the total number of CD34+ cells (x 10(6)) collected increased from 34 (+/- 6.3) to 52 (+/- 6.6) after two injections, 28 (+/- 3.6) to 65 (+/- 8.5) after three injections, and 28 (+/- 5.4) to 75 (+/- 18) after four injections of G-CSF. Further phenotyping demonstrated significant increases in CD34+HLA-DR+ cells with all three schedules relative to steady-state marrow. There were no changes in the total number of CD34+HLA-DR- cells after two and four shots; however, this population increased from 10 x 10(6) in steady-state marrow to 23 x 10(6) (p = 0.012) after three injections. Analysis of peripheral blood indicated a statistically significant increase in the circulating white count, but more interestingly, there were significant increases in the number of CD34+ cells x 10(4)/mL, suggesting the onset of mobilization. Steady-state blood contained a mean of 0.86 x 10(4)/mL CD34+ cells, which increased to 4.37 x 10(4)/mL, 7.43 x 10(4)/mL, and 8.62 x 10(4)/mL after two, three, and four injections, respectively-levels of CD34+ cells that are comparable to steady-state marrow. Reinfusion of a median of 1.6 x 10(6) activated CD34+ cells/kg resulted in the recovery of > 100/mm3 neutrophils and > 20,000 platelets by days 9 and 19, respectively, which was faster than our previous patients who received steady-state marrow, and comparable to our patients who received mobilized peripheral stem cells.