Progenitor and lymphoma cells in blood stem cell harvests: impact on survival following transplantation

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Abstract
This study evaluated whether cytokine-induced blood stem cell mobilization also mobilized lymphoma cells and whether lymphoma cell mobilization affected outcome post autologous blood stem cell transplant. Blood stem cell collections from 26 non-Hodgkin's lymphoma (NHL) patients harvested during steady-state (non-mobilized) and from 35 NHL patients harvested after cytokine administration (mobilized) were studied. The harvests were cultured and molecularly evaluated for clonal markers of the primary lymphoma. All patients underwent high-dose chemotherapy and autologous transplantation. Graft products from mobilized patients were more likely to contain lymphoma than graft products from non-mobilized patients (37% vs 19%) but this difference was not significant (P = 0.16). In a multivariate analysis, lymphoma contamination was not associated with patient age, gender, tumor grade, prior radiotherapy, duration of prior chemotherapy, mononuclear cell count, or the number of aphereses performed to obtain the product. Heavily pre-treated patients were less likely to have lymphoma-contaminated harvests (P = 0.064). Lymphoma contamination was positively associated with the number of progenitor cells collected (P = 0.047). In multivariate analyses, the only significant independent predictor of lymphoma contamination was the number of mononuclear cells collected (P = 0.031). Lymphoma contamination of transplanted apheresis products had no apparent impact on event-free and overall survival.