Translational Oncology (Aug 2017)

Dissecting the Biological Heterogeneity within Hormone Receptor Positive HER2 Negative Breast Cancer by Gene Expression Markers Identifies Indolent Tumors within Late Stage Disease

  • Jyothi S Prabhu,
  • Aruna Korlimarla,
  • C E Anupama,
  • Annie Alexander,
  • Rohini Raghavan,
  • Roma Kaul,
  • Krisha Desai,
  • Savitha Rajarajan,
  • Suraj Manjunath,
  • Marjorrie Correa,
  • R Raman,
  • Anjali Kalamdani,
  • MSN Prasad,
  • Shekar Patil,
  • K S Gopinath,
  • B S Srinath,
  • T.S. Sridhar

DOI
https://doi.org/10.1016/j.tranon.2017.04.011
Journal volume & issue
Vol. 10, no. 4
pp. 699 – 706

Abstract

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Hormone receptor positive (HR+) breast cancers are a heterogeneous class with differential prognosis. Although more than half of Indian women present with advanced disease, many such patients do well. We have attempted identification of biologically indolent tumors within HR+HER2- tumors based on gene expression using histological grade as a guide to tumor aggression. 144 HR+HER2- tumors were divided into subclasses based on scores derived by using transcript levels of multiple genes representing survival, proliferation, and apoptotic pathways and compared to classification by Ki-67 labeling index (LI). Clinical characters and disease free survival were compared between the subclasses. The findings were independently validated in the METABRIC data set. Using the previously established estrogen receptor (ER) down stream activity equation, 20% of the tumors with greater than 10% HR positivity by immunohistochemistry (IHC) were still found to have inadequate ER function. A tumor aggression probability score was used to segregate the remainder of tumors into indolent (22%) and aggressive (58%) classes. Significant difference in disease specific survival was seen between the groups (P = .02). Aggression probability based subclassification had a higher hazard ratio and also independent prognostic value (P < .05). Independent validation of the gene panel in the METABRIC data set showed all 3 classes; indolent (24%), aggressive (68%), and insufficient ER signaling (7%) with differential survival (P = .01). In agreement with other recent reports, biologically indolent tumors can be identified with small sets of gene panels and these tumors exist in a population with predominantly late stage disease.