Successful Mobilization of Peripheral Blood Stem Cells After Intensive Bendamustine Pre-Treatment In Patients with Multiple Myeloma

The alkylating agent bendamustine has structural similarities to both alkylating agents and purine analogs, and is effective in the treatment of patients with multiple myeloma. So far, no data are available on stem cell toxicity or on stem cell mobilization. Since autologous stem cell transplantation is an established treatment for multiple myeloma after primary treatment, we were interested in analysing the experience of stem cell mobilization after bendamustine treatment.

A retrospective analysis over a period of fifteen years was carried out in 56 (34 male and 22 female) patients with multiple myeloma after bendamustine pretreatment at the university hospitals Leipzig and Heidelberg. Patients had a median age of 58 (range 31–72) years. The median number of cycles was 3 (range 1–10) and the cumulative bendamustine dose ranged from 120 to 2400 mg/qm. The mobilization regimen in 37 cases was either cyclophosphamide 4 g/qm (n=33) or 7 g/qm (n=4) followed by G-CSF (2×5 ug/kg s.c.). Alternative regimens such as CAD, CED, TCED and others were used for mobilization in the remaining 19 patients. Apheresis was started as soon as peripheral blood CD34⁺ counts exceeded 10×10⁶/l with a harvest target of 4×10⁶ CD34⁺/kg using 4 times the blood volume. The minimal accepted target was 2×10⁶ CD34⁺/kg.

Stem cell harvest was successful in 54 of the 56 patients. In one patient the peripheral blood CD34+ cell count failed to reach 10 × 10⁶/l and no apheresis was performed. In one further patient a rapid decrease in peripheral blood CD34+ counts resulted in insufficient recovery of stem cells in the apheresis product. In 18 out of 54 patients (33%) the target was reached with a single apharesis. The median number of aphareses in the 54 patients was 2 (range 1–7) and the median CD34⁺ cell-count obtained was 5.5 (range 1.7–20.4) × 10⁶/kg. Engraftment was successful in 52/53 patients receiving a stem cell transplant. One patient was successfully harvested and did not receive the transplant yet.

From this retrospective analysis we conclude that mobilization of PBSC is possible after intensive bendamustine pretreatment.

Niederwieser:Bristol-Myers Squibb: Speakers Bureau; Novartis: Speakers Bureau. Goldschmidt:Celgene: Membership on an entity's Board of Directors or advisory committees; Ortho Biotech: Membership on an entity's Board of Directors or advisory committees; Ortho Biotech: Research Funding; Celgene: Research Funding; Chugai Pharma: Research Funding; Amgen: Research Funding.