{Reference Type}: Journal Article {Title}: Selecting postoperative adjuvant systemic therapy for early-stage breast cancer: An updated assessment and systematic review of leading commercially available gene expression assays. {Author}: Hyams DM;Bareket-Samish A;Rocha JEB;Diaz-Botero S;Franco S;Gagliato D;Gomez HL;Korbenfeld E;Krygier G;Mattar A;De Pierro AN;Borrego MR;Villarreal C; {Journal}: J Surg Oncol {Volume}: 0 {Issue}: 0 {Year}: 2024 Jun 24 {Factor}: 2.885 {DOI}: 10.1002/jso.27692 {Abstract}: Gene expression assays (GEAs) can guide treatment for early-stage breast cancer. Several large prospective randomized clinical trials, and numerous additional studies, now provide new information for selecting an appropriate GEA. This systematic review builds upon prior reviews, with a focus on five widely commercialized GEAs (Breast Cancer Index®, EndoPredict®, MammaPrint®, Oncotype DX®, and Prosigna®). The comprehensive dataset available provides a contemporary opportunity to assess each GEA's utility as a prognosticator and/or predictor of adjuvant therapy benefit.