HSCT Conditioning for Children: The Art in the Science

Hematopoietic stem cell transplantation (HSCT) is a therapeutic modality for pediatric malignancies and inherited and acquired hematological, immunological, and metabolic disorders. The efficacy of HSCT depends on many factors, including conditioning regimens, which are critical for eradicating malignant cells, suppressing the immune system to prevent graft rejection, and establishing an optimal microenvironment for engraftment.Conditioning methodologies have evolved from high-dose chemotherapy and total body irradiation to refined approaches that mitigate toxicity while maintaining their efficacy.The relationship between the conditioning regimen and donor selection influences short- and long-term transplant outcomes and minimizes adverse sequelae.With advances in molecular medicine, there is growing interest in chemotherapy-free conditioning protocols that leverage biological mechanisms to facilitate stem cell acceptance and minimize risks.The concept of "the art in the science" captures the intricate balance and decision-making essential for applying scientific principles to pediatric HSCT conditioning.Personalized medicine, expertise in regimen selection, and ethical considerations are key aspects of this approach.Examples include the customization of conditioning protocols, reduced-intensity conditioning, pharmacogenomics in personalized treatment, precision in drug sequencing and dosing, and innovations in serotherapy and chemo-free conditioning.We discuss historical perspectives, scientific foundations of conditioning, the role of radiation and serotherapy, and the potential shift toward <i>chemo-light</i> and <i>chemo-free</i> approaches.This review explores HSCT conditioning in pediatric patients, examining the scientific underpinnings and expertise required for protocol adaptation, challenges in resource-constrained environments, and evolving clinical demands.