A gene expression signature predicting the recurrence of tamoxifen-treated primary breast cancer.

A 36-gene classifier was constructed through expression profiling of 132 tumors from tamoxifen-treated patients using 70-mer oligonucleotide microarrays. The robustness of the signature was demonstrated using expression data from 83 independent tumors. The 36-gene signature was (i) more efficient to predict disease-free survival than the traditional histo-pathological prognostic factors, (ii) as effective as the Nottingham Prognostic Index or the "Adjuvant!" software, and (iii) the only independent prognostic factor. Comparison with several already published signatures demonstrated that the 36-gene signature was among the best to classify tumors. Keywords: Gene expression profiling; supervised analysis; molecular signature predictive of recurrence; univariate and multivariate analysis in relation to disease-free survival. In the study presented here, a cohort of 132 primary tumors from tamoxifen-treated patients followed up more than 5-years, was used to acquire expression profiles at the whole genome level by 70-mer oligonucleotide microarrays containing 22,680 probes (which represent 21,329 human specific genes). Supervised predictive analysis of microarrays allowed construction of a 36-gene molecular classifier whose robustness was assessed by using gene expression data from 83 independent tumors (including 23 tumors from our microarray platform and 60 tumors from the study by Ma et al., Cancer cell 2004; 5:607-616).