Lymphoplasmacytic lymphoma/immunocytoma: towards a disease-targeted treatment?

Lymphoplasmacytic-lymphoplasmacytoid lymphoma (LPL)/Waldenstrom's macroglobulinemia (WM) or immunocytoma (IMC) consists of diffuse proliferation of small mature B lymphocytes, plasmacytoid lymphocytes, and plasma-cells. The nosographic definition includes the lack of histological, immunophenotypic, cytogenetic, and molecular markers considered specific of other types of lymphoma. The cells show surface Ig (usually IgM), B-cell-associated antigens and display the CD5-, CD23- and CD10- phenotype, which allows for differential diagnosis from B-CLL and mantle cell lymphoma. t(9;14)(p13;q32) chromosomal translocation has been found in 50% of all LPL cases. The cytogenetic rearrangement juxtaposes the PAX-5 gene, which encodes for an essential transcription factor for B-cell proliferation and differention, to the Ig heavy chain gene. The combination of chlorambucil and prednisone holds as the standard treatment and seems to guarantee good control of the disease in most patients. Similar therapeutic results have been described with the combination of cyclophosphamide, vincristine, prednisone with (CHOP) or without doxorubicin (CVP), or with a combination of other alkylating agents and prednisone. Nucleoside analogues, alone or in combination with alkylating agents and anthracyclines, provide good salvage therapy for IMC and being increasingly employed as first line therapy. In a multicentric European trial Foran et al. administered the chimeric anti-CD20-monoclonal antibody (Rituximab) to 28 patients with previously treated IMC. Seven out of 25 evaluable patients (28%) achieved a partial response. Byrd et al. examined the outcome of 7 previously treated WM patients who received weekly infusions of rituximab (375 mg/m2). Therapy was well tolerated by all patients, and there was no decrease in cellular immune function, or significant infectious morbidity. Partial responses were noted in three of these patients, including two with fludarabine-refractory disease. These data suggest that rituximab exerts clinical activity on heavily pre-treated patients with WM. Furthermore, Weide et al. first reported that WM-associated polyneuropathy can be treated effectively with a combination of chemotherapy and the anti-CD20 monoclonal antibody rituximab. Most published trials exploring the efficacy of high dose treatment as salvage therapy for relapsed or refractory low grade non Hodgkin's lymphoma have included prevalently follicular or lymphocytic lymphomas. In selected high risk patients radioimmunotherapy with autologous stem-cell rescue, and myeloablative therapy followed either by autologous stem cell transplantation (SCT) or allogeneic SCT might represent an alternative strategy.