Abstract
Gene expression profiles offer the possibility of improving risk predication and optimizing treatment selection for individual patients. Two articles in this issue of the Journal describe clinical studies of gene expression profiling—one a developmental study and the other a validation study. Asgharzadeh et al. ( 1 ) address the development of a prognostic classifier for patients with metastatic neuroblastoma lacking amplification of the MYCN gene. Buyse et al. ( 2 ) report the validation of a gene expression–based prognostic classifier for patients with early breast cancer.