Peripheral Blood Stem Cell Collection In Patients Undergoing Induction Therapy with Lenalidomide Based Regimens: Failure Rates and Salvage Approaches

Lenalidomide based combinations are among the most common initial therapies for myeloma. Previous studies have suggested that lenalidomide therapy can result in suboptimal stem cell collection in patients eligible to undergo autologous stem cell transplantation, especially older patients after prolonged exposure to the drug. Many salvage approaches are used when attempting repeat stem cell collection in this patient group.

Two hundred twenty four patients who underwent stem cell collection following lenalidomide-dexamethasone induction from July 2004 and December 2009 were included in the current analysis. Data pertaining to the duration of lenalidomide therapy, stem cell mobilization regimen, and the collection yields were collected from the medical records.

The median age at mobilization was 60.6 years (range; 29, 76) and 136 (60%) were male. There were a total of 245 collection attempts from among 224 patients, 21 (9.8%) patients attempting to remobilize after failing to collect the desired numbers of stem cells at the first attempt. We first analyzed the results of the initial collection attempt. The median duration of lenalidomide therapy prior to stem cell collection was 4 months (range; 1, 26). The mobilization strategies were GCSF (Granulocyte Colony Stimulating Factor) alone in 151 (67%) patients, cyclophosphamide (CTX) followed by GCSF in 29 (13%) patients, and GCSF plus AMD3100 in 44 (20%) patients. Among those receiving AMD3100, it was added either due to peripheral blood CD34 cell count not reaching the threshold for initiation of harvest or for poor first day CD34 cells collection in 34 patients and given in a planned fashion in 10 patients. Overall 15 patients (7%) failed to reach the peripheral CD34 cell counts required to initiate apheresis, and among those starting apheresis 6 patients failed to collect at least 2 million CD34 cells/kg; a cumulative failure rate of 9%. Another 18 (8%) patients failed to collect at least 4 million CD34 cells /kg. The CD34 cells yield on day 1, the total yield, number of collections, the average daily yield and the percentage of the targeted cells collected for each mobilization strategy including failure rates are detailed in the table.

Twenty-one patients reattempted stem cell mobilization; including 14 that failed a first attempt and 7 did who not achieve the intended goal even though they collected more than 2 million CD34 cells/kg. The mobilization regimens were GCSF alone, CTX + GCSF, GCSF + GM-CSF (Granulocyte Macrophage Colony Stimulating Factor) and GCSF + AMD in 5, 8, 3, and 4 patients respectively. All patients collected at least 2 million CD34 cells /kg and 14 patients (70%) collected more than 4 million CD34 cells /kg. The median CD34 cells collected with the second attempt was 5.4 million/kg (rang; 2, 19.5) bringing the median total collection for these 21 patients to 9.6 million/kg (2.6-19.6). Overall, of the 224 patients studied, all but the 6 patients who failed initially and did not attempt a second collection collected at least 2 million CD34 cells /kg and 197 (88%) collected at least 4 million CD34 cells/kg.

While the overall failure rate of stem cell collection in patients receiving initial therapy with lenalidomide is 10%, a risk adapted approach of adding AMD3100 appear to decrease the risk of failure. However, majority of patients failing a stem cell harvest attempt can be salvaged with a second collection allowing these patients to proceed to a stem cell transplant if desired.

Gertz: Celgene: Honoraria; Millenium: Honoraria, Membership on an entity's Board of Directors or advisory committees; Genzyme: Research Funding. Lacy: Celgene: Research Funding. Dispenzieri: Celgene: Honoraria, Research Funding; Binding Site: Honoraria. Micallef: Genzyme: Membership on an entity's Board of Directors or advisory committees. Kumar: Celgene: Consultancy, Research Funding; Millennium: Research Funding; Merck: Consultancy, Research Funding; Novartis: Research Funding; Genzyme: Consultancy, Research Funding; Cephalon: Research Funding.