Comparison of Blood Graft Cellular Content in Myeloma (MM) Patients and Non-Hodgkin Lymphoma (NHL) Patients Mobilized with Chemotherapy Plus G-CSF with or without Plerixafor

Cellular composition of blood graft collected to support high-dose therapy may have important implications in regard to hematopoietic and immune reconstitution after high-dose therapy. Mobilization method used may have effect on graft composition as well as previous therapy given to the patients.

We have retrospective analyzed by flow cytometry cellular composition of freezed blood grafts in 34 patients with NHL (chemotherapy + G-CSF mobilization 15, add-on plerixafor 19 patients) and compared the observations with those of 17 MM patients mobilized either with low-dose cyclophosphamide + G-CSF (n=12) or with add-on plerixafor (n=5). The analyses were performed from the first graft collected from the chemomobilized patients or from the first draft collected after the plerixafor injection, respectively. Antibodies used included CD34, CD38, CD133 in regard to CD34⁺ subclasses and CD3, CD4, CD8, CD19 and CD3CD16/CD56 to analyze lymphocyte subsets. In addition, 7-aminoactinomycin D staining was used to assess the amount of nonviable CD34⁺ and lymphoid cells.

In regard to the patients mobilized without plerixafor, MM patients had higher content of CD34⁺ cells (4.9 vs. 2.0 × 10⁶/kg, p=0.009) as well as lower proportion of more primitive stem cells (0.8 vs. 1.9 % of all CD34⁺ cells, p=0.075) when compared to NHL patients. The amount of B-lymphocytes was also significantly higher in MM patients (0.5 × 10⁶/kg vs. 0.0, p< 0.001). No differences were observed in the total amount of T (CD3⁺) cells, NK cells or in the proportion of nonviable CD34⁺ or lymphoid cells. Of the plerixafor treated patients, the amount of B-lymphocytes was higher in MM patients (1.8 × 10⁶/kg vs. 0.0, p<0.001) as well as CD4/CD8 ratio (2.56 vs. 1.0, p=0.004) when compared to NHL patients.

As there appears to be differences between MM and NHL patients mobilized with or without plerixafor, it might be advisable to analyze separately effects of mobilization therapy to graft content and post-transplant outcomes in these diseases. Apparently the type and intensity of previous therapy given to the patients (e.g. rituximab) has important effects on graft cellular composition.

Jantunen:Genzyme: Has participated in EU Leadership meeting organized by Genzyme as well as Medical Advisory Board meeting organized by Genzyme Other, Honoraria. Silvennoinen:Genzyme: Consultancy.