Fernandez-Martinez, AranzazuPascual, TomásPerrone, GiuseppeMorales, Serafinde la Haba, JuanGonzález-Rivera, MilagrosGalván, PatriciaZalfa, FrancescaAmato, MichelaGonzalez, LuciaPrats, MiquelRojo, FedericoManso, LuisParé, LaiaAlonso, ImmaculadaAlbanell, JoanVivancos, AnaGonzález, AntonioMatito, JuditGonzález, SoniaFernandez, PedroAdamo, BarbaraMuñoz, MontserratViladot, MargaritaFont, CarmeAya, FranciscoVidal, MariaCaballero, RosalíaCarrasco, EvaAltomare, VittorioTonini, GiuseppePrat, AleixMartin, Miguel2025-01-072025-01-072017https://hdl.handle.net/10668/25130PAM50/Prosigna gene expression-based assay identifies three categorical risk of relapse groups (ROR-low, ROR-intermediate and ROR-high) in post-menopausal patients with estrogen receptor estrogen receptor-positive (ER+)/ HER2-negative (HER2-) early breast cancer. Low risk patients might not need adjuvant chemotherapy since their risk of distant relapse at 10-years is below 10% with endocrine therapy only. In this study, 517 consecutive patients with ER+/HER2- and node-negative disease were evaluated for Ki67 and Prosigna. Most of Luminal A tumors (65.6%) and ROR-low tumors (70.9%) had low Ki67 values (0-10%); however, the percentage of patients with ROR-medium or ROR-high disease within the Ki67 0-10% group was 42.7% (with tumor sizes ≤2 cm) and 33.9% (with tumor sizes > 2 cm). Finally, we found that the optimal Ki67 cutoff for identifying Luminal A or ROR-low tumors was 14%. Ki67 as a surrogate biomarker in identifying Prosigna low-risk outcome patients or Luminal A disease in the clinical setting is unreliable. In the absence of a well-validated prognostic gene expression-based assay, the optimal Ki67 cutoff for identifying low-risk outcome patients or Luminal A disease remains at 14%.enAttribution 4.0 Internationalhttp://creativecommons.org/licenses/by/4.0/Ki67PAM50/Prosignabreast cancerestrogen receptor-positive/HER2-negativeAntineoplastic Agents, HormonalBiomarkers, TumorBreast NeoplasmsChemotherapy, AdjuvantFemaleFollow-Up StudiesGene Expression ProfilingHumansIncidenceNeoplasm Recurrence, LocalPrognosisProspective StudiesReceptor, ErbB-2Receptors, EstrogenRisk AssessmentTamoxifenresearch article28423537open access10.18632/oncotarget.157481949-2553PMC5400635http://www.oncotarget.com/index.php?journal=oncotarget&page=article&op=view&path%5B%5D=15748&path%5B%5D=53674https://pmc.ncbi.nlm.nih.gov/articles/PMC5400635/pdf