A Better Mobilization Regimen for Newly Diagnosed Multiple Myeloma Patients,

Abstract Abstract 4051 Introduction: What constitutes an acceptable mobilization regimen for collecting CD34+ cells depends on whether the goal of collection is to obtain a minimum number versus optimal number of cells. When treating patients with high-risk myeloma it may be important to obtain an optimal number. Here we compare retrospectively our earlier mobilization regimen, VTD-PACE, with MVTD-PACE in newly diagnosed, previously untreated multiple myeloma patients. Materials and Methods : We reviewed data for all patients who collected hematopoietic progenitor cells on Total Therapy protocols TT3a/TT3b with VTD-PACE (n=394) from February 2004 to September 2008 (138 females and 256 males, median age 59y; range 31–75), and on TT4/TT5 with MVTD-PACE (n=188) from August 2008 to May 2011 (78 females and 110 males, median age 61y, range 30–76). Based on their predicted first day collection with a large volume leukapheresis (30L processed), using our center's predictive formula (Blood 2010; 116(21):1182a), patients were stratified into 4 mobilizer types: poor (<2×106 CD34+ cells/kg), intermediate (≥2 to 10×106), good (>10 to 20×106) and excellent (>20×106). Variables examined included number of CD34+ cells/μl blood on day 1 and day 2 of collection (we have a minimum 2 day collection requirement), number of collection days to reach our minimum goal of 20×106 CD34+ cells/kg, and total CD34+ cells/kg collected for both chemotherapy groups. Variables for both groups stratified by mobilizer type were compared using two-tailed student's t-tests, except for the poor mobilizer group, where population size was too small for formal statistical analyses (VTD-PACE n=7, MVTD-PACE n=4), although averages were calculated. Results : There was no significant difference between VTD-PACE and MVTD-PACE for CD34+ cells/μl blood on day 1 of collection among the excellent [mean 368.9 (n=184) vs. 434.6 x106 (n=92); p-value 0.07], good [mean 138.6 (n=102) vs. 128.6 x106 (n=40); p-value 0.19], and intermediate [mean 60.1 (n=100) vs. 55.9 x106 (n=52); p-value 0.39] groups. A statistically significant difference between VTD-PACE and MVTD-PACE was found for CD34+ cells/μl blood on day 2 of collection for excellent mobilizers [mean 333.8 (n=184) vs. 460 ×106 (n=92); p-value <0.001], but not for the good [mean 165.7 (n=102) vs. 189.5×106 (n=40); p-value 0.21] and intermediate [mean 80.1 (n=101) vs. 102.3 ×106 (n=52); p-value 0.07] groups. When CD34+ cell/kg collection totals with VTD-PACE and MVTD-PACE were compared, a significant difference was seen for the intermediate mobilizer group only [mean 23.6 (n=101) vs. 26.3 ×106 (n=52); p-value 0.03]. For the poor mobilizer group, VTD-PACE had an average CD34+ cells/μl blood of 13.5×106 for day 1 of collection and 17.0 ×106 for day 2, with a total of 14.5×106 CD34+cells/kg collected; while MVTD-PACE had an average of 13.2×106 CD34+ cells/μl blood for day 1 of collection, 24.9×106 for day 2, with a total of 24.2×106CD34+ cells/kg collected. The number of collection days was similar between VTD-PACE and MVTD-PACE in the excellent mobilization group (2 days), but was slightly more for VTD-PACE compared to MVTD-PACE for the good (2.1 vs. 2 days), intermediate (3.2 vs. 2.9 days), and poor (6.1 vs. 5.8 days) groups. Conclusion : Both regimens allow more than minimum collections, but MVTD-PACE provides a higher peak number of CD34+ cells/μl blood, resulting in a slightly lower mean number of days of collection than VTD-PACE to reach an optimal collection. Disclosures: No relevant conflicts of interest to declare.