The 21-gene recurrence score assay as a tool for predicting recurrence risk and guiding adjuvant treatment selection in early breast cancer
ABSTRACT Introduction Estrogen receptor-positive (ER+), HER2-negative breast cancer is the most common breast cancer subtype. While adjuvant endocrine therapy reduces recurrence risk, identifying which patients benefit from the addition of chemotherapy remains a key clinical challenge. The Oncotype DX® 21-gene Recurrence Score assay (Exact Sciences, via Genomic Health, Inc.) was developed to address this by quantifying distant recurrence risk and informing chemotherapy decisions in early-stage ER+/HER2− disease. Areas covered This diagnostic profile reviews the development, validation, and clinical evidence for Oncotype DX, including findings from the TAILORx and RxPONDER prospective trials and the subsequent development of hybrid tools integrating genomic and clinicopathological data. Alternative multiparameter molecular tests (MammaPrint, Prosigna, EndoPredict, Breast Cancer Index) are summarized and compared. We review international guideline recommendations, decision impact studies, cost-effectiveness evidence, and ongoing trials. Expert opinion Oncotype DX has strong prognostic evidence and has meaningfully reduced chemotherapy use, though its case as a biomarker predictive of therapeutic effect from chemotherapy rests on trial designs with important limitations. Its independent prognostic contribution beyond comprehensive clinicopathological assessment requires further clarification, and cost-effectiveness varies substantially by indication and healthcare setting.