Autologous stem cell transplantation in solid tumours of childhood.
High-dose chemoradiotherapy (HDCRT) followed by autologous stem cell (ASC) rescue is now widely used in a number of childhood malignancies. The most common to date is neuroblastoma, where it now has an established role as consolidation of initial complete remission in children over the age of 1 year with stage 4 disease. High-dose melphalan alone prolongs progression-free survival, with a small increase in long-term survival. The value of a total body irradiation (TBI)-based regimen is currently under randomized evaluation. In soft-tissue sarcoma, such as rhabdomyosarcoma or Ewing's sarcoma of bone or soft tissue, high-dose therapy has been used to consolidate initial complete or partial remission. The benefit has not been demonstrated in randomized studies but chemotherapy-alone regimens based on combined alkylating agents appear to be of potential value. Other tumours have been treated in this way but the place of high-dose therapy remains entirely unclear. It is possible that inherently chemosensitive tumours, such as Wilm's tumour, may be candidates where standard treatment has failed. The replacement of bone marrow reinfusion with cytokine-primed peripheral blood stem cell (PBSC) rescue has reduced the morbidity of these procedures. The issue of the potential risk of reinfusing tumour cells has been addressed in neuroblastoma where purging using immunodepletion or in vitro chemotherapy has been carried out.