 In an early proof-of-principle pilot study of single agent neoadjuvant docetaxol, we identified a predictive gene expression pattern, and, using leave-one-cross validation, a method of internal validation, we demonstrated that the pattern was likely to accurately discriminate between responders and non-responders Chang, J.C., et al., Gene expression profiling for the prediction of therapeutic response to docetaxel in patients with breast cancer. Lancet, 2003. 3629381: p. 362-9. A similar pilot study of neoadjuvant AC undertaken by a collaborator in the UK suggests that different profiles will be predictive for AC response. 