Gene Expression Test Identifies Patients Who Can Skip Chemotherapy

For decades, classification of tumor type, decisions about treatment, and estimation of prognosis have been based on pathology inspection of tumor tissue — but with varying accuracy. New “gene expression” technologies can determine which genes are active (making mRNA and protein) in any tissue, including tumor samples. Can such tests offer more accurate predictions than traditional pathology examination?

The value of a widely used commercial assay that assesses the activity of 21 genes to predict chemotherapy benefit was tested in women with hormone-receptor–positive, human epidermal growth factor receptor-2 (HER2)–negative, axillary node–negative breast cancer. Previous studies have shown that women with high scores on the assay benefit fro…