HER HER 2 equivocal breast cancer that is positive by alternative probe HER HER 2 FISH FISH are classified as HER HER 2 negative by Oncotype DX DX

摘要

Abstract In breast cancer, human epidermal growth factor receptor 2 ( HER 2) status is determined by immunohistochemistry ( IHC ) and/or in?situ hybridization. Oncotype DX also reports HER 2 status by an rt‐ PCR ‐based assay. Assay concordance between IHC and fluorescent in?situ hybridization ( FISH ) (including alternative probe HER 2 FISH ) vs Oncotype DX HER 2 rt‐ PCR has not been described in the post‐2013 American Society of Clinical Oncology/College of American Pathologists ( ASCO / CAP ) HER 2 Guideline revision setting. We performed a retrospective review of HER 2 equivocal invasive breast carcinoma from 2014 to 2016 with the Oncotype DX HER 2 result. Fifteen patients with HER 2 equivocal invasive breast cancer had Oncotype DX performed. Of these, 13 underwent alternative probe HER 2 FISH yielding 4 negative, 6 equivocal and 3 positive results. All 15 cases were classified as HER 2 negative by Oncotype DX rt‐ PCR , including the three cases which were positive by alternative probe HER 2 FISH , yielding a discordance rate for Oncotype DX rt‐ PCR HER 2 of 20% (3/15). All three patients with HER 2‐positive breast cancer on the basis of alternative probe HER 2 FISH received anti‐ HER 2‐targeted therapy. Treatment decisions based on HER 2 status should utilize the IHC / FISH result as Oncotype DX results may incorrectly disqualify some patients from being eligible for anti‐ HER 2 therapy based on the current 2013 ASCO / CAP HER 2 Guidelines.