Limiting lenalidomide exposure and rescue plerixafor can eliminate Haematopoietic stem cell (HPC) first collection failure in Bortezomib, Lenalidomide and dexamethasone (VRD) treated and transplant eligible Multiple Myeloma (MM) patients

Abstract

Aim: A retrospective analysis to assess whether the timing of HPC collection prior to greater than 6-weeks of lenalidomide with or without the use of rescue plerixafor reduces primary HPC collection failures in MM.

Method: MM first attempt autologous HPC mobilisation patients were eligible included(n=111). Three sub-groups were assessed to compare HPC collection outcomes: Group 1-Pharmaceutical benefit scheme (PBS) plerixafor and >6-weeks weeks lenalidomide(n=45), Group2-Lenalidomide <6-weeks (n=29, PBS plerixafor and Group 3-Lenalidomide exposure <6-week, rescue plerixafor (n=37). Demographic data and outcomes measured included: Disease response, prior radiotherapy, collection days, HPC mobilisation failures, CD34 pre-counts and yield. Mobilisation schedule was filgrastim 10mcg/kg 4 nights and pre-count day 5. In group 3, plerixafor was administered at 10pm for next day collection if day 5 CD34 was <14x 10^6/L or the estimated first day CD34 yield was less than half the total target. In groups 1 and 2, a failing mobilisation could not be rescued. Collection proceeded if the CD34 was >18x10^6/L. Clinician discretion was used for cyclophosphamide 1.5g/m2 mobilisation at first attempt. Inability to proceed to apheresis or collection of insufficient cells for a single HPC autograft (<2-3x10^6/kg) defined collection failure. Medians of demographic data and collection outcomes were compared using Kruskal-Wallis and group proportions were calculated with Fisher Exact test contingency tables.

Results: The 3 treatment groups were comparable for demographic data, prior radiotherapy, response and collection targets. Cyclophosphamide for HPC mobilisation was more frequent in Groups 1 and 2 (p0.008). Primary HPC mobilisation/collection failure rates were higher in group 1, 19/25, compared to group 2, 4/25 failures, (p = .011). The combination of rescue plerixafor and limiting lenalidomide exposure (group 3) reduced collection failures to zero (4/24 in group 2 vs 0/37 failures in group 3, p = .033). Median collection days were lower in group 3, at 1 day compared to group 2 (1.5 days) and group 1 (2 days) respectively, p0.0273. CD34 pre-counts on day 1 of collection were higher in group 3, 49x10^6/L compared to 29 x10^6/L in group 2 and 19x10^6/L in group 1, p0.00. Total CD34 yield was significantly higher with plerixafor rescue(group3), than group 2 or 1, (7.44x10^6/kg, 6.04x10^6/kg, 5.18x10^6/kg respectively), p0.0019.

Conclusion: The combination lenalidomide exposure <6-weeks and the use of rescue plerixafor can eliminate HPC primary collection failure in MM, minimising wasted chair bookings and treatment delays. The CD34 yield was higher, cyclophosphamide exposure and collection days were lower using this collection algorithm.