Abstract 4409

Introduction:

PBPC mobilization with intermediate-dose cyclophosphamide (3–4 gm/m2) (ID-CY) and G-CSF when compared to low-dose CY (1–2 gm/m2)-based strategies, has been shown to have a favorable risk/benefit profile in MM patients (pts) receiving novel induction therapies (Hamadani M. BBMT 2012). However the relative efficacy of ID-CY as compared to plerixafor in PBPC mobilization in MM pts is not known. Herein we report outcomes of ID-CY/G-CSF mobilization compared to plerixafor/G-CSF mobilization in MM pts treated with novel induction regimens.

Methods:

This multicenter outcomes study includes 84 pts who underwent a planned, single autograft within 1-year of starting induction therapy with novel chemotherapy agents (thalidomide, lenalidomide, bortezomib) from 2003–2012. Consecutive pts undergoing mobilization with ID-CY/G-CSF (3–4 gm/m2) (n=55) at one institution were compared against consecutive pts receiving plerixafor/G-CSF (0.24 mg/kg) (n=29) at a different transplant center. At baseline the two groups were compared for parameters predicting mobilization failure. In order to assess efficiency of PBPC mobilization, we evaluated peak peripheral blood (PB) CD34+ cell counts, CD34+ cell yield on day1 of collection, total CD34+ cell collection, and total number of apheresis sessions. Mobilization failure was defined as failure to collect ≥2 ×106 cells/kg body weight. All pts with normal renal function received uniform conditioning with Mel200 (MEL140 if serum creatinine was ≥2 mg/dl).

Results:

At baseline, the ID-CY and plerixafor cohorts were well balanced (Table 1). No difference was observed in the use of lenalidomide (p=0.3). Compared to plerixafor, ID-CY use was associated with higher median peak PB CD34+ cell count (63/μl vs. 160/μl, p=0.01), CD34+ yield on day 1 of collection (6.5 ×106/kg vs. 11.7 ×106/kg, p=0.004), and total CD34+ cell yield (10.5 ×106/kg vs. 24.9 ×106/kg, p=0.001). Median numbers of apheresis sessions were 2.2 in each group (p=0.9). No mobilization failures were seen in either group. There was no difference in the proportion of pts collecting ≥5×106/kg CD34+ cells in either group (93% vs. 96%, p=0.6), but more pts in ID-CY cohort collected ≥10×106/kg CD34+ cells (55% vs. 78%, p=0.02). Neutrophil engraftment was significantly faster (9.9 days vs. 13.1 days, p<0.001) in the ID-CY pts, likely because of higher infused CD34+ cell dose. Rate of adverse events were higher in the ID-CY cohort including neutropenic fevers (p=0.02), intravenous antibiotic use (p=0.03), hospitalization (p=0.05) and packed red cell transfusions (p=0.007).

Conclusion:

In the era of novel agents compared to plerixafor, ID-CY produced a more robust PBPC mobilization, faster engraftment, but was associated with significantly higher (but manageable) toxicity, and no difference in mobilization failure rates. These data support use of either ID-CY or plerixafor-based PBPC mobilization in MM pts undergoing stem cell collection following novel induction therapies.

Table 1.

Baseline characteristics.

Baseline characteristics.

1Defined as hypodiploidy or deletion 13 on conventional cytogenetics or presence of t(4;14), t(14:16), -17p on FISH and/or conventional cytogenetics.

2Percentages do not add up 100% since some pts received more than 1 novel agent either in combination or during different lines of therapy.

Disclosures:

Awan:Allos Therapeutics: Speakers Bureau. Hamadani:Conquer Cancer Foundation of ASCO: Research Funding; ASBMT & Millennium New Investigator Award: Research Funding; American Cancer Society 116837-IRG-09–061-01: Research Funding; Celgene Corp: Speakers Bureau.

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