Lourdes Calvo, Brandy Pitcher, Chun-Yang Fan, Álvaro Rodríguez-Lescure, Lisa A. Carey, Blanca Munárriz, William T. Barry, Eric P. Winer, Eva Carrasco, Marc L. Citron, Aleix Prat, Nuria Ribelles, Maggie C.U. Cheang, Elaine R. Mardis, MC Liu, Manuel Ruiz-Borrego, Jose Ignacio Chacon, A. Arcusa, Rafael Caballero, Joan Albanell, E. Alba, Tammi L. Vickery, Matthew J. Ellis, Joel S. Parker, A. Lluch, Clifford A. Hudis, Yufeng Li, Miguel Angel Seguí-Palmer, Ángel L Guerrero, Barbara Adamo, Arrate Plazaola, Margaret L. Gulley, Miguel Martin, Octavio Burgues, José A. López, Maria Vidal, Zhiyuan Hu, Charles M. Perou, Universitat de Barcelona, [Prat,A, Adamo,B, Vidal,M.J] Translational Genomics Group, Vall D'Hebron Institute of Oncology (VHIO) Barcelona, Spain. [Prat,A] Department of Medicine, Universitat Autònoma de Barcelona, Spain. [Lluch,A, Burgues,O] Department of Medical Oncology, Department of Pathology, Hospital Clínico Universitario de Valencia, Spain. [Albanell,J] Department of Medical Oncology, Hospital Del Mar, IMIM, Barcelona, Spain. [Albanell,J] Department of Medical Oncology, Universitat Pompeu Fabra (UPF), Barcelona, Spain. [Barry,W.T] Department of Biostatistics and Computational Biology, Dana-Farber Cancer Institute, Boston, MA, United States. [Fan,C, Parker,J.S, Cheang,M.C.U, Li,Y, Hu,Z, Gulley,M.L, Carey,L.A, Perou,C.M] Lineberger Comprehensive Cancer Center, University of North Carolina, Chapel Hill, NC, United States. [Chacón,J.I] Department of Medical Oncology, Hospital Virgen de la Salud, Toledo, Spain. [Parker,J.S, Perou,C.M] Department of Genetics, University of North Carolina, Chapel Hill, NC, United States. [Calvo,L] Department of Medical Oncology, Complexo Hospitalario Universitario de A Coruña, A Coruña, Spain. [Plazaola,A] Department of Medical Oncology, Onkologikoa, San-Sebastián, Spain. [Arcusa,A] Department of Medical Oncology, Consorci Sanitari de Terrassa, Barcelona, Spain. [Seguí-Palmer,M.A] Department of Medical Oncology, Corporació Sanitària Parc Taulí, Sabadell, Spain. [Ribelles,N, Alba,E] Department of Medical Oncology, Department of Pathology, Hospital Universitario Virgen de la Victoria, Málaga, Spain. [Rodríguez-Lescure,A] Department of Medical Oncology, Hospital General de Elche, Alicante, Spain. [Guerrero,A] Department of Medical Oncology, Instituto Valenciano de Oncología (IVO), Valencia, Spain. [Ruiz-Borrego,M] Department of Medical Oncology, Hospital Universitario Virgen Del Rocío, Sevilla, Spain. [Munarriz,B] Department of Medical Oncology, Hospital Universitario la Fe, Valencia, Spain. [López,J.A] Department of Medical Oncology, Hospital San Camilo, Madrid, Spain.[Pitcher,B.N] Alliance Statistical and Data Center, Duke University, Durham, NC, United States. [Liu,M.C] Department of Oncology, Mayo Clinic, Rochester, MN, United States. [Citron,M.L] ProHEALTH Care Assoc., LLP, Lake Success, NY, United States. [Ellis,M.J, Mardis,E, Vickery,T] Department of Oncology, Washington University St. Louis, MO, United States. [Hudis,C.A] Department of Medicine, Memorial Sloan Kettering Cancer Center, New York, NY, United States. [Winer,E.P] Medical Oncology, Dana-Farber Cancer Institute, Boston, MA, United States. [Caballero,R, Carrasco,E, Martín,M] GEICAM (Spanish Breast Cancer Research Group), Madrid, Spain. [Martín,M] Department of Medical Oncology, Instituto de Investigación Sanitaria, Hospital Universitario Gregorio Marañón, Madrid, Spain. [Perou,C.M] Department of Pathology and Laboratory Medicine, University of North Carolina, Chapel Hill, NC, United States., and This work was supported by funds from the NCI Breast SPORE program Grant No. P50-CA58223-09A1 (CMP), by RO1-CA138255 (CMP), by the Breast Cancer Research Foundation (CMP and MJE), National Cancer Institute (NCI) Strategic Partnering to Evaluate Cancer Signatures Grant No. U01 CA114722-01 (MJE), by the Sociedad Española de Oncología Médica (AP), by FEDER (RETICC-RD12/0036/0051, RD12/0036/0042, RD12/0036/0076, RD12/0036/0070), by Instituto de Salud Carlos III—PI13/01718 (AP), by Banco Bilbao Vizcaya Argentaria (BBVA) Foundation (AP) and by the Alliance Statistics and Data Center (U10-CA33601).