Limitations in predicting PAM50 intrinsic subtype and risk of relapse score with Ki67 in estrogen receptor-positive HER2-negative breast cancer
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Aranzazu Fernandez-Martinez1,2, Tomás Pascual1,2, Giuseppe Perrone3, Serafin Morales4, Juan de la Haba5, Milagros González-Rivera6, Patricia Galván1,2,7, Francesca Zalfa3, Michela Amato3, Lucia Gonzalez8, Miquel Prats9, Federico Rojo10, Luis Manso11, Laia Paré1,2, Immaculada Alonso1, Joan Albanell12, Ana Vivancos7, Antonio González13, Judit Matito7, Sonia González14, Pedro Fernandez1, Barbara Adamo1,2, Montserrat Muñoz1,2, Margarita Viladot1,2, Carme Font1,2, Francisco Aya1,2, Maria Vidal1,2, Rosalía Caballero15, Eva Carrasco15, Vittorio Altomare3, Giuseppe Tonini3, Aleix Prat1,2,7, Miguel Martin6
1Medical Oncology Department, Hospital Clínic of Barcelona, Barcelona, Spain
2Translational Genomics and Targeted Therapeutics in Solid Tumors, August Pi i Sunyer Biomedical Research Institute, Barcelona, Spain
3Department of Medicine, Università Campus Bio-Medico di Roma, Rome, Italy
4Medical Oncology Deparment, Arnau de Vilanova de Lleida Universitary Hospital, Lleida, Spain
5Medical Oncology Department, Reina Sofía University Hospital, Cordoba, Spain
6Medical Oncology Department, Instituto de Investigación Sanitaria Gregorio Marañón (IISGM), Universidad Complutense, Madrid, Spain
7Vall d'Hebron Institute of Oncology, Barcelona, Spain
8Medical Oncology Department, Quirón Hospital, Madrid, Spain
9Master of Breast Pathology, University of Barcelona, Barcelona, Spain
10Pathology Department, Fundación Jiménez Díaz Health Research Institute (IIS-FJD), Madrid, Spain
11Medical Oncology Department, Doce de Octubre Hospital, Madrid, Spain
12Medical Oncology Department, Hospital del Mar, Barcelona, Spain
13Medical Oncology Department, MD Anderson Cancer Center, Madrid, Spain
14Medical Oncology Department, Mutua de Terrassa Hospital, Barcelona, Spain
15Spanish Breast Cancer Research Group Grupo Español de Investigación en Cáncer de Mama (GEICAM), Madrid, Spain
Miguel Martin, email: firstname.lastname@example.org
Aleix Prat, email: email@example.com
Keywords: PAM50/Prosigna, breast cancer, Ki67, estrogen receptor-positive/HER2-negative
Received: October 19, 2016 Accepted: January 27, 2017 Published: February 27, 2017
PAM50/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%.
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