Targeted Intensification by a New Preparative Regimen for Patients With Low-Grade B-Cell Lymphoma Utilizing Standard-Dose Yttrium-90 Ibritumomab Tiuxetan (Zevalin) Radioimmunotherapy (RIT) Combined With High-Dose Beam Followed by Autologous Stem Cell Transplantation (ASCT)

The indolent course of the low-grade B-cell lymphoma is thus characterized by multiple remissions and relapses with ever-shortening "time to progression" intervals, and by ultimately becoming refractory to treatment. In this situation of recurrences, intensive therapy including high-dose chemotherapy or chemo-radiotherapy followed by autologous hematopoietic stem cell transplantation appears as a therapeutic option. With the use of peripheral blood stem cell, the autologous stem cell transplantation (ASCT) procedure has become easier and cheaper, and it has a mortality rate of below 5% and manageable morbidity. EBMT registry data or institution driven studies have shown an improvement in event free survival when compared to chemotherapy in relapsing patients. Recently Schouten et al reported in a randomized study a significant benefit in survival for patients submitted in relapse to ASCT. Consolidation with ASCT has been studied in first line treatment and showed a significant improvement in survival in one randomized study. BEAM regimen is a referent high-dose chemotherapy used in intensive therapy followed by ASCT in the treatment of malignant lymphoma. It could therefore be considered for patients with indolent lymphoma if it could be shown to improve survival. In most studies the conditioning regimen was associating chemotherapy and Total Body Irradiation (TBI) for indolent lymphoma as it is very sensitive to even low dose of radiotherapy. TBI however is time consuming and technically not available in all transplant centers and associated with some long term toxicities; a search for more specific targeted irradiation has been a goal for several years.

Recently, a new preparative regimen for older patients with aggressive CD20-positive B-cell lymphoma utilizing standard-dose 0.4 mCi/kg 90Y ibritumomab tiuxetan combined with high-dose BEAM followed by ASCT showed a CR rate of 92% with a follow-up of 9 months. Finally, high-dose radioimmunotherapy with 90Y ibritumomab tiuxetan and high-dose cyclophosphamide/etoposide followed by ASCT for poor-risk or relapsed B-cell NHL have been reported, with a 2-year DFS of 80%. The use of conventional dose of Yttrium did not need heavy radioprotection procedures, and can be widely distributed in transplant centers.

Overall toxicities were comparable to standard autologous transplantation conditioning regimens, and the combined treatment was well tolerated. The hematological reconstitution after transplantation occurred without delay, except in two cases than in control-based high-dose chemotherapy alone population. Mucositis and neutropenic fever were reported without increase of severity. Nonhematological adverse events have been observed, three interstitial pneumonitis, mild abnormalities on liver or kidney function tests, except one case of veno-occlusive disease, and 4 fatal infection (disseminated aspergillosis with a brain abscess, streptococcal sepsis, staphylococcal sepsis, and disseminated varicella zoster).

Therefore, all these data support a phase II trial evaluating efficacy and toxicities in patients with low grade B-Cell lymphoma of a new preparative regimen combining a standard dose 90Y ibritumomab tiuxetan and high-dose BEAM chemotherapy followed by ASCT.