PS1534 EFFICACY AND SAFETY OF STEM CELL MOBILISATION FOLLOWING GDP SALVAGE IN PATIENTS WITH RELAPSED OR REFRACTORY LYMPHOMA
Authors: Tang C. , Espin‐Garcia O. , Prica A. , Kurkreti V. , Kridel R. , Keating A. , Patriquin C. , Kuruvilla J. , Crump M. 
Published: June 2019

Background:

High‐dose chemotherapy and autologous stem cell transplant (ASCT) remains a key treatment strategy in patients with relapsed/refractory (R/R) aggressive lymphoma. CCTG study LY.12 established gemcitabine, dexamethasone and cisplatin (GDP) as a standard salvage chemotherapy regimen for R/R lymphoma across Canada. Peripheral blood stem cell (PBSC) mobilisation on this salvage regimen can be achieved using granulocyte colony‐stimulating factor (GCSF) during salvage (GDP) or following an additional course of cyclophosphamide and etoposide (CE) at completion of salvage GDP; however these strategies have yet to be compared.

Aims:

To compare the efficacy and safety of PBSC mobilisation with GDP to our previous standard of CE since GDP was adopted as standard salvage therapy for R/R lymphoma.

Methods:

All patients undergoing PBSC mobilisation following salvage GDP for R/R lymphoma from January 2012 to August 2018 were included in this analysis. CE comprised C 2 g/m2 d1, E 200 mg/m2 d 1–3, and GCSF 10 μg/kg d4–12, with apheresis planned d13. For collection following GDP, GCSF was added 10 μg/kg d9–14, apheresis starting d15. Apheresis started when the blood CD34 count was ≥10 cells/μl, with target collection of ≥5 x 106 CD34+ cells/kg. From May 2014 plerixafor 24 μg/kg was added to GCSF in the event of slow or inadequate mobilisation. Primary outcomes were PB CD34+ count on planned day of apheresis and total CD34+ yield. Secondary outcomes included number of apheresis days, febrile neutropenia after mobilisation, time to engraftment, days admitted for transplant, blood product usage, PFS and OS.

Results:

A total of 339 patients underwent PBSC mobilisation, 210 following GDP and 129 after CE. Patients in the GDP group had more delays from planned to actual day of collection (mean 0.7 vs 0.4 days, p = 0.006) and required more total days of apheresis (median 2 vs 1 day; p = 0.001). The percentage of GDP patients collected on planned day of harvest and who required only one day of apheresis were 71% and 50% respectively, versus 84% and 69% respectively after CE. ROC curves (Figure 1) for platelets, neutrophils and PB CD34+ measured on planned day of collection confirm PB CD34+ as the best predictor for successful attainment of target CD34+ yield. In multivariable analysis, CE led to both higher PB CD34+ count on planned day of harvest and higher total CD34+ yield (both p < 0.001), despite a higher rate of plerixafor use in the GDP group (37/210 vs 6/129). However, when considering a target total CD34+ yield ≥5x106/kg there was no difference between mobilisation regimens (p = 0.66). Similarly, on multivariable analysis, days to engraftment, ASCT admission duration and platelet transfusions required showed no statistical difference between the two mobilisation strategies; patients mobilised with CE required more RBC transfusion during ASCT (p = 0.04). Of interest, prior bone marrow involvement and use of plerixafor were both predictors for longer engraftment time (p = 0.013 and p = 0.007 respectively), after adjustment for mobilisation and CD34+ yield. Although total CD34+ yield was not associated with days to engraftment on multivariable analysis, it was independently associated with blood product usage and day 100 blood count recovery. In multivariable Cox analyses, disease status at time of ASCT was the main predictor of PFS and OS.

Summary/Conclusion:

While CE/GCSF appears to be a more efficient method of mobilisation in patients undergoing GDP salvage for R/R lymphoma, this did not translate to significant differences in clinical outcomes such as engraftment or duration of hospital admission.

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