Variables Predicting for Poor Mobilization of Peripheral Blood Stem Cells (PBSC) in Newly Diagnosed Myeloma Patients, Treated on TT-2 Protocol.

Autotransplantation is now considered the standard of care for myeloma patients ≤ 65 years. Tandem autotransplants result in doubling of the percentage of patients alive and event-free at 7 years when compared to a single transplant (IFM-94). A minimum number of 2 x 10⁶/kg CD34 cells is required per transplant for reliable engraftment. The aim of this study was to identify variables associated with the inability to collect sufficient numbers of PBSC for tandem transplants. 668 recently diagnosed patients were enrolled in our TT-2 protocol consisting of intensive induction with VAD, DCEP, CAD and DCEP followed by tandem transplants. PBSC were collected after CAD plus hematopoietic growth factors (either G-CSF or GM-CSF). 49 patients (7.5%) failed to collect ≥ 4 x 10⁶/kg CD34 cells (poor mobilizers) and the characteristics of these patients were compared to those of 77 patients who collected > 30 x 10⁶/kg CD34 cells (excellent mobilizers) using chi-square tests. A multivariate analysis was performed using a stepwise logistic regression. The median number of CD34 cells collected in the group of poor mobilizers was 2.1 x 10⁶/kg (range 0–3.9) in a median of 3 days (range 1–9). In the group of excellent mobilizers the median number of CD34 cells was 38.7 x 10⁶/kg (range 30.1–86) in a median of 2 days (range 1–4). Baseline and mobilization variables significantly different between these 2 groups are listed in Table 1. On multivariate analysis duration of cytopenia (platelets < 50,000/μl and/or neutrophils < 1,000/μl) > 7 days (OR: 27; p<0.0001), randomization to thalidomide (OR 4.5; p=0.007), age ≥ 65 years (OR: 4.96; p=0.01), female gender (OR: 3.62; p=0.02), and neutropenic infection requiring intraveneous antibiotics (OR 3.8; p=0.03) were independently associated with poor collection. No differences in event-free (p= .68) or overall survival (p=.73) were observed between the excellent and poor mobilizers. These data confirm our previous observations of inferior collection in older patients and in those receiving thalidomide as part of upfront therapy. The duration of cytopenia after chemotherapy is a good reflection of patient’s stem cell reserve, while administration of broad spectrum antibiotics prior to collection has been shown to be myelosuppressive. The negative impact of female gender on the ability to collect well is new.