Predominant or complete recipient T-cell chimerism following alemtuzumab-based allogeneic transplantation is reversed by donor lymphocytes and not associated with graft failure.

The clinical significance of mixed chimerism following allogeneic haematopoietic stem cell transplantation (HSCT) remains controversial. Its relevance and incidence are probably influenced by the conditioning regimen and incorporation of T-cell depletion. The presence of recipient chimerism levels >40-50% following T-cell replete reduced intensity transplantation correlates with a high risk of graft rejection, regardless of donor-lymphocyte infusions, but it is unclear whether this finding translates to T-cell depleted transplants. We conducted a retrospective single-institution analysis of patients receiving alemtuzumab-based HSCT. 27/152 (18%) evaluable cases had predominantly recipient T-cell chimerism at 3 months or beyond. By contrast, coincident chimerism in the granulocyte lineage was predominantly of donor origin (median 100%) in all but one patient. Donor lymphocyte infusion effectively converted predominantly recipient T-cell chimerism to ful donor chimerism in all evaluable cases including three cases with no detectable donor T cells. The only graft failure occurred in the patient with predominantly recipient myeloid chimerism in whom rejection occurred rapidly before donor lymphocytes could be administered. We conclude that predominant or complete recipient T-cell chimerism following alemtuzumab-based regimens does not have the same clinical implications as that following T-cell replete transplants and can be effectively converted with donor lymphocytes without the need for lympho-depleting agents or re-conditioning.

Rituximab in combination with CODOX-M/IVAC: a retrospective analysis of 23 cases of non-HIV related B-cell non-Hodgkin lymphoma with proliferation index >95%.

The safety and efficacy of rituximab with CODOX-M/IVAC (cyclophosphamide, doxorubicin, vincristine, methotrexate/ifosfamide, etoposide, high dose cytarabine) was retrospectively analysed in 23 patients with non-human immunodeficiency virus-related B-cell non-Hodgkin lymphoma with proliferation index >95% [14 with classical Burkitt lymphoma (BL), five with B-cell lymphoma unclassifiable, with features intermediate between diffuse large B cell lymphoma (DLBCL) and BL, and four with DLBCL]. Six (26%) low-risk (LR) patients received three cycles of CODOX-M and 17 (74%) high-risk (HR) cases were assigned to four cycles of alternating CODOX-M/IVAC. Rituximab 375 mg/m² was infused on days 1 and 10 of each cycle. Toxicity was comparable to that reported with CODOX-M/IVAC, with no treatment-related death. Two patients developed grade 3 rituximab-induced delayed neutropenia, with no adverse outcome. After completing treatment, 83% LR patients and 71% HR patients achieved CR by positron emission tomography-computerized tomography (PET-CT). Three (13%) patients received salvage treatment. At a median follow-up of 34 months (range = 18-75), 19 (83%) patients (100% LR and 74% HR) were alive, including one case undergoing salvage for late relapse. Four HR patients (17%) had died, three from primary progressive disease and one from treatment-refractory relapse 2 months after achieving CR. These results with R-CODOX-M/R-IVAC compare favourably with existing data using CODOX-M/IVAC and warrant further prospective studies. The potential pitfalls of PET-CT to assess response are highlighted.