A new minimally ablative stem cell transplantation procedure in high-risk patients not eligible for nonmyeloablative allogeneic bone marrow transplantation

Pulmonary complications of haematopoietic cell transplantation in children

Paediatric haematopoietic cell transplantation has experienced significant advances in the last few decades. However, pulmonary complications are an important limitation to the efficacy of this intervention, contributing to post-transplantation morbidity and mortality. Such complications persist even in experienced centres and occur in adult and paediatric recipients. This review identifies the paediatric pulmonary complications that are commonly seen following haematopoietic cell transplantation and addresses both infectious and non-infectious aetiologies and their clinical manifestations, evaluation, and potential therapy. Ultimately, improvement in outcomes will require attention to immunosuppression as well as traditional diagnostic procedures and treatment. This article aims to review the current state of pulmonary complications post-transplantation, to examine the impact of our recent advances and changes in treatment, and to identify potential future therapies and hypothesise what role these might have on long-term survival.

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.

Nonmyeloablative stem cell transplantation and cell therapy for malignant and non-malignant diseases

The conditioning prior to allogeneic stem cell transplantation was originally designed as a myeloablative conditioning, designed to eliminate malignant or genetically abnormal cells and then use the transplant procedure for rescue of the patients or to replace missing bone marrow products. However, allografts can induce effective graft vs. malignancy effects and can also eliminate undesirable hematopoietic stem cells in patients with genetic disorders and autoimmune diseases, thus documenting that alloreactive effects mediated by donor lymphocytes post-grafting can play a major role in eliminating hematopoietic cell of host origin, as well as provide effective immunotherapy for the treatment of disease recurrence. The efficacy of donor lymphocyte infusion (DLI) could be improved by activation with rIL-2 or by donor immunization. The cumulative experience over the years suggesting that alloreactive donor lymphocytes were most effective in eliminating tumor cells of host origin resulted in an attempt to reduce the intensity of the conditioning in preparation for the transplant procedure used for the treatment of hematological and other malignancies as well as life-threatening non-malignant disorders for which allogeneic stem cell transplantation may be indicated. Our working hypothesis proposed that the myeloablative conditioning which is hazardous and may be associated with early and late side effects, may not be required for treatment of patients with any indication for allogeneic stem cell transplantation. Instead, nonmyeloablative conditioning based on the use of reduced intensive preparatory regimen, also known as nonmyeloablative stem cell transplantation, may be sufficient for engraftment of donor stem cells while avoiding procedure-related toxicity and mortality, followed by elimination of undesirable cells of host origin by post-transplant effects mediated by alloreactive donor lymphocytes infused along with donor stem cells or administered subsequently as DLI. Improvement of the immediate outcome of stem cell transplantation using NST due to a significant decrease in transplant related mortality has broadened the spectrum of patients eligible for allogeneic stem cell transplantation, including elderly patients and other patients with less than optimal performance status. Likewise, the safer use of stem cell transplantation prompted expanding the scope of potential indications for allogeneic stem cell transplantation, such as metastatic solid tumors and autoimmune disorders, which now are slowly becoming much more acceptable. Current strategies focus on the need to improve the capacity of donor lymphocytes to eliminate undesirable malignant and non-malignant hematopoietic cells of host origin, replacing abnormal or malignant stem cells or their products with normal hematopoietic stem cells of donor origin, while minimizing procedure-related toxicity and mortality and improving the quality of life by reducing the incidence and severity of hazardous acute and chronic GVHD.