Jan W. Gratama

PURPOSE: Half the patients with acute myeloid leukemia (AML) who achieve complete remission (CR), ultimately relapse. Residual treatment-surviving leukemia is considered responsible for the outgrowth of AML. In many retrospective studies, detection of minimal residual disease (MRD) has been shown to enable identification of these poor-outcome patients by showing its independent prognostic impact. Most studies focus on molecular markers or analyze data in retrospect. This study establishes the value of immunophenotypically assessed MRD in the context of a multicenter clinical trial in adult AML with sample collection and analysis performed in a few specialized centers. PATIENTS AND METHODS: In adults (younger than age 60 years) with AML enrolled onto the Dutch-Belgian Hemato-Oncology Cooperative Group/Swiss Group for Clinical Cancer Research Acute Myeloid Leukemia 42A study, MRD was evaluated in bone marrow samples in CR (164 after induction cycle 1, 183 after cycle 2, 124 after consolidation therapy). RESULTS: After all courses of therapy, low MRD values distinguished patients with relatively favorable outcome from those with high relapse rate and adverse relapse-free and overall survival. In the whole patient group and in the subgroup with intermediate-risk cytogenetics, MRD was an independent prognostic factor. Multivariate analysis after cycle 2, when decisions about consolidation treatment have to be made, confirmed that high MRD values (> 0.1% of WBC) were associated with a higher risk of relapse after adjustment for consolidation treatment time-dependent covariate risk score and early or later CR. CONCLUSION: In future treatment studies, risk stratification should be based not only on risk estimation assessed at diagnosis but also on MRD as a therapy-dependent prognostic factor.

Recipients of a partially T-cell-depleted (TCD) allogeneic stem cell transplantation (allo-SCT) developing reactivation of Epstein-Barr virus (EBV) with quantified viral DNA levels exceeding 1000 genome equivalents/milliliter (geq/mL) are at high risk for EBV-lymphoproliferative disease (EBV-LPD). We studied whether preemptive therapy with rituximab prevents EBV-LPD, LPD-mortality, and abrogates viral reactivation in high-risk patients. We monitored 49 recipients of a TCD allo-SCT weekly for EBV reactivation by quantitative real-time polymerase chain reaction (PCR). Preemptive therapy by a single infusion of rituximab was given to patients with viral reactivation more than or equal to 1000 geq/mL. Results were compared with an historical control group of patients retrospectively monitored for EBV reactivation at similar intervals. There were 17 prospectively monitored patients who showed EBV reactivation more than or equal to 1000 geq/mL and 15 received preemptive therapy. Median time to preemptive therapy was 113 days (range, 41-202 days) after SCT. There were 14 patients who showed complete response (CR) as characterized by prevention of EBV-LPD and complete clearance of EBV-DNA from plasma, which was achieved after a median number of 8 days (range, 1-46 days). One patient progressed to EBV-LPD despite preemptive therapy, but obtained CR after 2 infusions of rituximab and donor lymphocyte infusion. There were 2 patients who had already developed EBV-LPD prior to preemptive rituximab, but obtained CR following 2 rituximab infusions. Comparison of this prospectively followed series to our historical cohort with the same high-risk profile showed a reduction of EBV-LPD incidence (18% +/- 9% versus 49% +/- 11%, respectively) and a complete abrogation of LPD-mortality (0% versus 26% +/- 10%, respectively) (P =.04) at 6 months from EBV-DNA more than or equal to 1000 geq/mL. Frequent quantitative monitoring of EBV reactivation and preemptive therapy by rituximab improves outcome in patients at high risk of EBV-LPD. (Blood. 2002;99:4364-4369)

Reactivation of the Epstein-Barr virus (EBV) after allogeneic stem cell transplantation (allo-SCT) may evoke a protective cellular immune response or may be complicated by the development of EBV-lymphoproliferative disease (EBV-LPD). So far, very little is known about the incidence, recurrence, and sequelae of EBV reactivation following allo-SCT. EBV reactivation was retrospectively monitored in 85 EBV-seropositive recipients of a T-cell--depleted (TCD) allo-SCT and 65 EBV-seropositive recipients of an unmanipulated allo-SCT. Viral reactivation (more than 50 EBV genome equivalents [gEq]/mL) was monitored frequently by quantitative real-time plasma polymerase chain reaction until day 180 after SCT. Probabilities of developing viral reactivation were high after both unmanipulated and TCD-allogeneic SCT (31% +/- 6% versus 65% +/- 7%, respectively). A high CD34(+) cell number of the graft appeared as a novel significant predictor (P =.001) for EBV reactivation. Recurrent reactivation was observed more frequently in recipients of a TCD graft, and EBV-LPD occurred only after TCD-SCT. High-risk status, TCD, and use of antithymocyte globulin were predictive for developing EBV-LPD. Plasma EBV DNA quantitatively predicted EBV-LPD. The positive and negative predictive values of a viral load of 1000 gEq/mL were, respectively, 39% and 100% after TCD. Treatment-related mortality did not differ significantly between TCD and non-TCD transplants, but the incidence of chronic graft-versus-host disease was significantly less in TCD patients. It is concluded that EBV reactivation occurs frequently after TCD and unmanipulated allo-SCT, especially in recipients of grafts with high CD34(+) cell counts. EBV-LPD, however, occurred only after TCD, and EBV load quantitatively predicted EBV-LPD in recipients of a TCD graft. (Blood. 2001;98:972-978)