Re: Limits of predictive models using microarray data for breast cancer clinical treatment outcome.

Abstract
The ability to accurately predict outcome to tamoxifen therapy would advance the management of breast cancer. Tamoxifen acts through the estrogen receptor (ER), and ER expression levels are currently the best predictors of response. Last year, Ma et al. ( 1 ) reported a novel biomarker of a two-gene expression ratio (HOXB13 to IL17BR) in 60 patients with ER-positive early-stage breast cancer treated with adjuvant tamoxifen. However, recently, Reid et al. ( 2 ) failed to validate the performance of this two-gene predictor. We would like to point out three problems with the study of Reid et al. ( 2 ) : 1) cohort selection, 2) definition of response, and 3) primer design.