Hematology & Oncology HSCT in Pediatric Patients

Hematopoietic stem cell transplantation (HSCT), also known as a bone marrow transplant, is used to treat both malignant and non-malignant conditions. Graft can be collected from bone marrow, cord, or peripheral blood. Stem cells' ability to differentiate and self-renewal can suppress malignant cells or replace dysfunctional cells in non-malignant conditions like hemoglobinopathies or immunodeficiencies. Hematopoietic stem cells can be derived from either the patient (autologous) or an allogeneic donor. Unlike solid organ transplants, the main criteria for allogenic donor selection are based on human leukocyte antigen (HLA) compatibility. HLA genes are highly polymorphic; thus, these differences can result in an allo-immune reaction, which can cause graft rejection. In terms of HLA compatibility donor and recipient can be fully matched or a haploidentical match. Fully matched Donors can be categorized into three groups: the preferred option is matched sibling donors; however, if not accessible, related donors or even less preferred option, unrelated donors, will be considered. Before graft injection, a combination of chemotherapies with or without total body irradiation (TBI), also known as a conditioning regimen, is used to eradicate the primary disease in case of malignancy or create a space for stem cells to engraft. The conditioning regimen is designed to suppress the recipient's immune system to protect the injected stem cells from allo-immune reactions. This can make the patient more prone to infections, so to prevent it, antimicrobial medications are also deployed, alongside conditioning. Post-HSCT, patients will be monitored for viral, bacterial, or fungal infection, early graft rejection, and graft versus host disease. To ensure early engraftment, patients' chimerism will be monitored through Short Tandem Repeat Polymerase Chain Reaction (STR-PCR) or fluorescence in situ hybridization (FISH) tests from bone marrow or peripheral blood. GvHD is a condition where the donor's white blood cells recognize host cells as foreigners and attack them. To manage this, immunosuppressant medications are prescribed as prophylaxis or treatment. While HSCT can be life-saving in both adult and pediatric patients, the overall outcomes are more favorable in pediatric patients due to the prevention of disease in early stages and less organ damage.