Cure of a patient with profoundly chemotherapy-refractory primary mediastinal large B-cell lymphoma: Role of rituximab, high-dose therapy, and allogeneic stem cell transplantation

Allogeneic Stem Cell Transplantation Provides Durable Remission in Patients with Primary Mediastinal Large B Cell Lymphoma

Standard therapy for relapsed or refractory (rel/ref) primary mediastinal large B cell lymphoma (PMBCL) is salvage therapy followed by autologous (auto) hematopoietic stem cell transplantation (HSCT). However, many patients have refractory disease and are unable to undergo autoHSCT, and a sizeable proportion of patients will relapse after autoHSCT. By analogy to diffuse large B cell lymphoma, these patients may be treated with allogeneic (allo) HSCT with curative intent, but at the risk of significant morbidity and mortality. Given the advent of effective immunotherapy approaches for rel/ref PMBCL, it is important to better understand the toxicity and efficacy of alloHSCT in these patients, to which these new approaches could be an alternative. Therefore, we retrospectively studied the outcomes of alloHSCT in a multicenter cohort of 28 patients with rel/ref PMBCL who underwent transplantation at 4 centers. Most patients (79%) were sensitive to pretransplantation therapy and 86% received reduced-intensity conditioning. The overall progression-free survival (PFS), overall survival (OS), and cumulative incidences of nonrelapse mortality and relapse in the cohort at 5 years were 34%, 45%, 32%, and 33%, respectively. Outcomes were significantly better in patients with pretransplantation responsive disease (2-year PFS and OS of 50% and 58%, respectively) compared with refractory patients (2-year PFS and OS of 0%). In our multicenter retrospective study, alloHSCT produced durable remissions in a proportion of patients with treatment-sensitive disease before transplantation (5-year PFS of 44%) and should be considered in the treatment of patients with rel/ref PMBCL.

Treatment of primary mediastinal large B cell lymphoma with an alternating chemotherapy regimen based on high-dose methotrexate

Primary mediastinal large B cell lymphomas (MLCL) differ from other diffuse large cell lymphomas, leading to a description as a separate entity in the current World Health Organization classification. Dose intensification improves long-term results, but no standard therapy has been established so far. We investigated the use of a high-dose methotrexate-based alternating chemotherapy regimen (B-ALL protocol of the German ALL study group) followed by consolidative mediastinal radiotherapy first as a single-center trial, then later as a prospective multicenter trial in 44 patients with a median age of 33 years. Response rates exceeded 90% with an overall survival rate of 80% in the single-center group (8.6 years median follow-up) and 82% in the multicenter group (2.5 years follow-up).Short-term toxicity was manageable, but required hospitalization: the rates of grade 3 or 4 toxicity were 20% (for mucositis), 42% (for neutropenia), 29% (for thrombocytopenia), and 9% (for neutropenic fever). No relapse occurred more than 2 years after diagnosis and initiation of treatment, but unfortunately, no patient with overt progression or relapse within these 2 years could be salvaged. Future directions in the treatment of MLCL will not focus on further dose intensification, but rather on the incorporation of (radio)immunotherapy as a therapeutic tool and gene expression profiling as well as positron emission tomography-computed tomography as stratifying tools.

Allogeneic hematopoietic stem cell transplantation in the elderly

The development of reduced intensity or non-myeloablative conditioning (NST) in preparation for allogeneic stem cell transplantation (SCT) revolutionized the field and led to reconsideration of the dogma of upper age limit that was set up by the transplant centers as an eligibility parameter. Analysis of the literature data showed that NST regimens are associated with decreased transplant related mortality, and graft-versus-host disease, in comparison with standard myeloablative conditioning, in patients above the age of 50-55 years, or in younger patients with significant comorbidities. However we have to mention, that our considerations are based on the retrospective analysis of the literature data, and that well controlled prospective randomized studies are needed in order to definitely assess the role of NST. Comorbidity indices might be proved as the most important parameters for the choice of the most proper regimen for each patient in need and should be included in future trials.

Hematopoietic stem cell therapy for malignant diseases

Allogeneic bone marrow or blood stem cell transplantation (SCT) has changed its face in the last two decades. The introduction of nonmyeloablative conditioning regimens has reduced procedure toxicity and allowed the application of SCT in patients and conditions in which SCT was not offered in the past. In this review we will summarize the changes and accomplishments achieved in the past years in the field of stem cell transplantation for malignant disorders.