Maintenance Rituximab after Autologous Stem Cell Transplant for High-Risk B-Cell Lymphoma Induces Prolonged and Severe Hypogammaglobulinemia.
Authors: Lim Seah H. , Zhang Yana , Wang Zhiqing , Esler William V. , Beggs David , Pruitt Brian , Hancock Paul , Townsend Mary 
Published: April 2020

Abstract
Rituximab, a chimeric CD20 antibody, has been incorporated in various chemotherapy regimen for B-cell lymphoma. It has also been used as maintenance therapy in some of these patients. However, the effects of its long-term use on the immune system has not been previously documented. Here, we present our preliminary analysis of the effect of maintenance rituximab therapy on the B-cell immune repertoire in nine consecutive patients with B-cell lymphoma who were treated with maintenance rituximab after autologous stem cell transplant (ASCT) for high-risk disease.
Nine patients (seven men and two women) with high-risk B-cell lymphoma were treated. Their diagnosis were: advanced mantle cell lymphoma in first CR (6), Stage IV DLCL in CR1 (1) and high grade NHL in CR2 (2). Median age was 66 years (range 38–72 years). CR was achieved using R-CHOP (8) or R-DHAP (1). Autologous stem cells were harvested during hematopoietic recovery from the last course of chemo-immunotherapy and G-CSF. Within two weeks after stem cell harvest, each patient received intravenous melphalan (200 mg/m2) following by the infusion of at least 2 x 106/kg CD34+ cells. All patients received a rituximab infusion (375 mg/m2) every three months starting D+100 after ASCT for a total of 2 years or until disease relapse. Unlike patients who underwent ASCT without rituximab, in whom B-cell recovery occured between 3–6 months, we observed severe delays in the immunoglobulin recoveries in these patients. At 9 months after transplant, all patients were IgM and IgG deficient, with only 1/9 patient acheived a normal IgA level. Even at 24 months after transplant, all patients were still IgM deficient and only 20% achieved normal IgA and IgG levels. The severity of immuno-deficiencies was next examined. We observed severe immunoglobulin deficiency (defined by &lt; 50% normal levels) in IgM in all patients and in IgG and IgA in more than 20% patients at 24 months, suggesting that the immunoglobulin recovery was both delayed and severely affected.
The severe immunoglobulin deficiencies may be clinically relevant. One patient developed two episodes (follow-up of 12+ months), one seven episodes (follow-up 28+ months) and another two episodes of chest infection and a vancomycin-sensitive chronic diarrhea (follow-up 18+ months). All three patient had severe and prolonged immunoglobulin deficiencies. With a median follow-up of 27 months (range 12–31 months), all patients have remained lymphoma-free.
These preliminary results, therefore, suggest that rituximab administration every three months after autologous transplant for high-risk B-cell NHL delays immunoglobulin recovery and may be associated with increased risks of infection. Although this approach may reduce lymphoma relapse, careful monitoring of the immunoglobulin recovery and interventional as appropriate should be done routinely in these patients.