Reduced-intensity hematopoietic stem cell transplantation (RIST) for solid malignancies.

Reduced intensity stem cell transplantation (RIST) is a new approach of stem cell transplantation, which has shown promising features as reported in multiple phase I and II studies. Elderly patients, who are not eligible for conventional myeloablative hematopoietic stem cell transplantation (HSCT), are now treatable with RIST. It has also reduced regimen-related toxicity and provided better prognosis in short-term follow-up than conventional HSCT. Among solid tumors, metastatic renal cell carcinoma was found to respond well to RIST. Clinical studies are currently being conducted to evaluate the efficacy of RIST in other types of solid tumors. However, the mechanism of graft-versus-host disease (GVHD) and graft-versus-tumor (GVT) effects remains unclear. More knowledge on the mechanism is crucial to enhance the antitumor effect and to improve the prognosis further.