Updated Results of the Mayo Clinic Risk Adapted Algorithm for Peripheral Blood Stem Cell Mobilization Utilizing G-CSF and Plerixafor

Background:  The likelihood of successful mobilization has improved with the addition of Plerixafor to G-CSF in ASCT.  Due to its high cost, risk adapted algorithms were instituted to identify patients who would benefit from plerixafor. 

Methods:  The current algorithm was instituted in December 2009. Mobilization commences with GCSF alone; plerixafor is added if day 4 PBCD34 is <10/µL for single transplant, <20/µL for multiple transplants, day 1 yield is <1.5 million CD34/kg, or subsequent yield is < 0.5 million CD34/kg.  Goal of collection varied by disease and by number of intended transplants (3-5 million CD34/kg/transplant).  The results of this mobilization strategy are presented here.

Results:  We studied 1080 mobilizations in 1068 patients using the current protocol between June 2010 and December 2013; 548 MM (50%), 327 NHL (30%), 144 amyloidosis or light chain deposition disease (AL/LCD; 13%) and 61 Hodgkin’s (13%). Overall, 55.4% of patients required plerixafor; (MM 58%, NHL 61%, AL/LCD 35%, HL 46%). The majority of pateints initiated plerixafor on day 4 for low PB CD34 count; 19% started beyond 4 days for suboptimal CD34 collection.  There was no difference between the diagnoses in terms of the need to initiate plerixafor for low PB CD34 or for suboptimal CD34 collection.  Median days of plerixafor was 2 (IQR 1-3); 42% and 22% required > 2 days and > 3 days, respectively.  More patients with NHL (50%) needed > 2 days of plerixafor vs MM (41%), HL (40%) and AL/LCD (23%); p = 0.004. The median number of CD34 cells collected was 7.4 million/kg (IQR 5.2- 9.9).  Median CD34 collection was highest for MM and AL/LCD, reflecting the practice to collect for more than one transplant.  Overall 9 (<1%) and 22 (2%) patients collected < 2 million and < 2.5 million CD34 cells/kg, respectively.  More patients with NHL (4%) collected < 2.5 million/kg compared with MM (1%), AL/LCD (2%) and HL (0%), p=0.02. The median number of days of apheresis was 2 (IQR 1-3) and was higher in the NHL group (p=0.002). The median CD34 collected per day was 3.6 million/ kg (IQR 2-5.8); higher in MM and AL/LCD vs NHL and HL (p < 0.001).  The median CD34 collection was very similar for those patients getting plerixafor versus those not requiring plerixafor (p=0.26).  The median time to ANC and platelet engraftment were 14 days (IQR 13-16) and 13 days (IQR 12-15), respectively.  While there was no difference in ANC engraftment, platelet engraftment was longer among patients requring plerxiafor.

Conclusion: This data confirms the effectiveness of this risk adapted algorithm in over 1000 patients over 4 years.  The mobilization failure rate remains low.  Approximately 45% of pateints did not require plerixafor, supporting the use of this risk adapted algorithm to select apprpriate patients who require plerixafor.