Utility of Second and Subsequent Peripheral Blood Stem Cell (PBSC) Mobilization in Myeloma Patients
Authors: Kulkarni Samar , Bloor Adrian JC , Dennis Mike , Sweeney Dianne , Angelica Rita , Grantham Sarah , Donaghey Siobhan , Leather Angela , Ashton Lyndsey , Cavet James 
Published: October 2019

Abstract
Abstract 4401
Standard therapy for myeloma includes induction therapy followed by high dose melphalan and autograft (HDM/autograft). Safe delivery of HDM requires optimum peripheral blood stem cells (PBSC) as quantitated by CD34 expression. In ability to collect sufficient PBSC is not uncommon and efficacy of subsequent harvest after failed first attemp needs evaluation. In this single centre analysis, 62 patients with myeloma treated at our centre between 1997 and 2009 were analysed to assess the results of second and subsequent harvest and the factors predictive of failure to mobilize CD34 cells more than 2×10^6/kg. 40 patients were male and 22 were females with a median age of 57 yr. (range: 41–68, M:56yr. Vs. F: 58 yr., p=0.6) Before first harvest patients received induction therapy with either VAD (or similar) chemotherapy to maximum response (n=46), thalidomide combination (n=15) or combination (n=2) and only 2 patients had exposure to Melphalan. 49 patients (78%) achieved at least PR with induction therapy. For the first harvest mobilization was attempted with Cyclo/GCSF (n=56), ESHAP (n=5) and GCSF alone (n=1) at a median interval of 38 days from finishing induction (range: 15–535). Median CD34 yield after first attempt was 1.7×10^6/kg (range: 0.04–14.6) in 1 (n=52) or 2 (n=10) collects. 28 patients (45%) achieved yield more than 2. Yield was slightly lower in female patients (1.39 vs. 2.58, p=0.074) but there was no effect of age, type of chemotherapy, response or mobilization regimen. 28 patients had back to back mobilization with either Cyclo/GCSF or ESHAP priming at a median of 35 d from first harvest (range: 11–99) and the median CD34 yield was 1.7(range: 0.03–14.7) in 1(n=19) or 2 (n=9) collects. All other patients had second harvest at a median of 1018 d(range: 25–2246) and 21 had the collection attempted after HDM/Autograft. The median CD34 yield in the entire cohort of 62 patients was 2.4 (range: 0.03–27.2) and this was achieved in 1(n=45) or 2 (n=17) procedures. Patients who had HDM/autograft (n=21) achieved same yields as others (median: 2.8 vs. 2.2, p=0.11) and required similar number of procedures (median: 1, p=0.62). 26/62 patients (42%) achieved more than 2×10^6 yield in second attempt. Rate was lower in HDM group but not statistically significant (28% vs. 51%, p=0.13). 12/62 (19%) had third attempt at harvest at a median of 862 days from second harvest. The median CD34 yield was 2.3 (range: 0.09–4.13) and 6 (50%) achieved yield more than 2×10^6/kg. There was no correlation between CD34 yield in first and subsequent harvests (R^2: 1.2%). Out of 26 patients who did not collect more than 2 in first attempt, only 9 (35%) managed to achieve this yield in second attempts, especially if they had HDM/autograft. This single centre analysis shows that failure to achieve sufficient CD34 cells in first attempt results in low yields in subsequent tries at PBSC mobilization. If this is a predictor of disease behaviour will be analysed. For patients who may be candidates for more than one HDM procedures efforts to increase the yield in first attempt should be tried. Impact of newer drugs on the attempts at subsequent mobilization needs evaluation.

Disclosures:
No relevant conflicts of interest to declare.