Immunochemotherapy, in Vivo Purging, PBSC Mobilization and Autotransplant in Relapsed or Refractory Follicular Lymphoma

Autologous stem cell transplantation has been shown effective in the long-term control of follicular lymphoma. Lymphoma, however, can progress after high-dose treatments. Lymphoma cells have been proved to contaminate bone marrow and peripheral blood stem cells (PBSC) collections and may contribute to relapse after autotransplant. The presence in peripheral blood and marrow of PCR-detectable cells bearing the bcl-2 rearrangement appeared to be a surrogate marker of disease and the achievement of a bcl-2 negative status is associated with a lower risk of recurrence. Several methods have been attempted to abolish graft contamination: in vitro treatment with cytotoxic agents, in vitro treatment with anti-B-cell monoclonal antibodies and complement, immunomagnetic beads, positive selection of CD34+ cells. All these techniques usually produce loss of cells, are time-consuming and expensive, and neoplastic depletion is often partial with residual polymerase chain reaction (PCR)-positive cells in the graft. In the last years the chimeric anti-CD20 monoclonal antibody Rituximab has been shown to be an effective therapeutic option for low-grade lymphoma. Owing to the different mechanism of action, the synergism with cytotoxic agents, and the non-overlapping toxicity, Rituximab is an ideal drug for combination with chemotherapy. On this basis, Rituximab has been used during mobilisation procedures as a tool to obtain in vivo purging and collection of lymphoma-free progenitor cells. In addition, several studies have demonstrated that the efficiency of peripheral blood stem cells (PBSC) harvested is not adversely affected by Rituximab and that engraftment and all parameters of hematopoietic recovery are not compromised. The incorporation of Rituximab into sequential high-dose therapy programs produced high rates of clinical and molecular remission in patients with indolent lymphoma, indicating that the antibody has an additive effect on chemotherapy.