Predicting breast cancer behavior by microarray analysis

In the treatment of breast cancer, patient-tailored therapy is becoming increasingly important. Decisions on optimal treatment include the choice between mastectomy and breast-conserving treatment; dose of radiotherapy; and decisions on adjuvant chemotherapy and hormonal therapy. Gene expression profiling by microarray analysis allows the study of the level of expression of large numbers of mRNAs in a single experiment. Gene expression analysis can be used to subclassify tumors on the basis of hierarchical cluster analysis in specific subgroups; supervised cluster analysis can be used to directly link gene expression profiles to clinical characteristics, including prognosis and response to various forms of treatment. We have used microarray analysis, first on a series of 117 breast carcinomas and more recently on a series of 295 breast carcinomas. We have defined a gene expression profile of 70 genes that is predictive for a short interval to distant metastases.