Mobilization of peripheral blood progenitor cells (PBPC) in patients undergoing chemotherapy followed by autologous peripheral blood stem cell transplant (SCT) for high risk breast cancer (HRBC)

We have determined the effect of delayed addition of G-CSF after chemothera py on PBPC mobilization in a group of 30 patients with high risk breast can cer (HRBC) undergoing standard chemotherapy followed by high-dose chemother apy (HDCT) and autologous SCT. Patients received FAC chemotherapy every 21 days followed by G-CSF at doses of 5 mu g/kg/day starting on day +15 (group s 1 and 2) or +8 (group 3) after chemotherapy, PBPC collections were perfor med daily starting after 4 doses of G-CSF and continued until more than 2.5 x 10(6) CD34(+) cells had been collected. In group 1, steady-state BM prog enitors were also harvested and used for SCT, Groups 2 and 3 received PBPC only. The median number of collections was three in each group. Significant ly more PB CD34(+) cells were collected in patients receiving G-CSF startin g on day 8 vs day 15 (9.43 x 10(6)/kg and 6.2 x 10(6)/kg, respectively) (P < 0.05). After conditioning chemotherapy all harvested cells including BM a nd PBPC were reinfused, Neutrophil and platelet engraftment was significant ly faster in patients transplanted with day 8 G-CSF-mobilized PBPC (P < 0.0 5) and was associated with lower transplant related morbidity as reflected by days of fever, antibiotics or hospitalization (P < 0.05). Both schedules of mobilization provided successful long-term engraftment with 1 year post -transplant counts above 80% of pretransplant values. In conclusion, we dem onstrate that delayed addition of G-CSF results in successful mobilization and collection of PBPC with significant advantage of day 8 G-CSF vs day 15. PBPC collections can be scheduled on a fixed day instead of being guided b y the PB counts which provides a practical advantage. Transplantation of su ch progenitors results in rapid short-term and long-term trilineage engraft ment.