An analysis of the optimal timing of peripheral blood stem cell harvesting following priming with cyclophosphamide and G-CSF

Increasing demand on the apheresis service makes efficient harvesting of peripheral blood stem cells (PBSCs) essential. A total of 168 adult patients with haematological malignancy were primed using low–moderate dose cyclophosphamide (1.5–3 g/m2) with G-CSF 5–10 μg/kg per day. Harvesting was booked and peripheral blood (PB) counts first checked between 6 and 10 days post-priming. One hundred and thirty (77%) patients harvested successfully (total harvest yield ⩾2 × 106 CD34+/kg) and the median PBSC collection per procedure was 2.18 × 106/kg (range 0.1–14.5). Only more lines of prior chemotherapy predicted failure to harvest in multivariate analysis (P=0.003). The PB CD34+ cell count correlated significantly with harvest yield (r=0.8448, P<0.0001). A PB CD34+ count ⩾10/μl predicted a collection of ⩾2 × 106/kg (positive-predictive value of 61%, negative-predictive-value 100%). Patients first attending day 9 required significantly fewer visits to achieve a successful harvest than those first attending days 6–8 without increasing the risk of failure. No significant difference in failure rates, number of days attending and total harvest yield was found between days 9 and 10 attendees. Collection from day 9 may however enable higher target yields to be achieved. PB CD34+ count monitoring should commence and harvesting booked from day 9 to optimize both the harvest and the efficiency of the PBSC harvesting service.