Gene expression profiling (GEP) is being used increasingly for risk stratification to identify women with lymph node-negative, estrogen receptor-positive, early stage breast cancer who are most likely to benefit from adjuvant chemotherapy. The authors of this report evaluated the cost effectiveness of recurrence score-guided treatment using 2 commercially available GEP tests, Oncotype DX (Genomic Health, Redwood City, Calif) and MammaPrint (Agendia Inc., Irvine, Calif), from a third-party payer's perspective.