Limited human epidermal growth factor receptor 2 discordance in metastatic breast cancer patients treated with trastuzumab, a population based study

Eur J Cancer. 2014 Mar;50(5):885-91. doi: 10.1016/j.ejca.2014.01.010. Epub 2014 Jan 31.

Abstract

Background: Accurate assessment of the human epidermal growth factor receptor 2 (HER2) in breast cancer is essential for proper treatment decisions. HER2 positivity confirmation rates in breast cancer trials by central testing pathology laboratories were reported to be approximately 85%. The aim of our study was to assess in a population based sample concordance of HER2 status in metastatic breast cancer (MBC) patients locally tested HER2 positive and treated with trastuzumab. Moreover cost-effectiveness of in situ hybridisation (ISH) in patients with an immunohistochemical score 3+ (IHC3+) was explored.

Methods: MBC patients treated between 2005 and 2009 with trastuzumab-based therapy in North East Netherlands were identified by a survey of hospital pharmacies. Primary tumour samples were retested centrally for HER2 status using 1 immunohistochemical (IHC) method and two methods using ISH on tissue micro-arrays. Potential discordant patients were retested on whole tumour slides. HER2 positivity was defined as: (1) ISH amplification (according to American Society of Clinical Oncology/College of American Pathologists (ASCO/CAP) clinical practice Guideline Update) and (2) when ISH failed an IHC score of 3+. Cost-effectiveness was estimated using potential ISH and treatment costs.

Results: HER2 status could be retested in 174 of 194 (90%) patients. The HER2 concordance rate was 87%. The 21 discordant patients were in the 67% due to primary HER2 testing with only IHC. Overall survival of HER2 discordant and concordant patients was not significantly different (18 versus 25months, p=0.131). Structural ISH in the case of IHC3+ has an estimated potential saving of €87,710 per 100 patients.

Conclusion: HER2 concordance in a population based study is comparable to those described in selected populations. Discordance is mostly due to testing with only IHC. ISH in the case of IHC3+ is cost-effective.

Keywords: HER2 concordance; HER2 positive breast cancer; HER2 testing; Immunohistochemistry; In situ hybridisation; Trastuzumab.

Publication types

  • Multicenter Study

MeSH terms

  • Adult
  • Aged
  • Aged, 80 and over
  • Antibodies, Monoclonal, Humanized / therapeutic use*
  • Breast Neoplasms / drug therapy*
  • Breast Neoplasms / genetics
  • Breast Neoplasms / metabolism
  • Cost-Benefit Analysis
  • Female
  • Humans
  • Immunohistochemistry
  • In Situ Hybridization / economics
  • In Situ Hybridization / methods
  • In Situ Hybridization, Fluorescence / economics
  • In Situ Hybridization, Fluorescence / methods
  • Kaplan-Meier Estimate
  • Middle Aged
  • Neoplasm Metastasis
  • Netherlands
  • Outcome Assessment, Health Care / methods
  • Population Surveillance / methods
  • Receptor, ErbB-2 / genetics
  • Receptor, ErbB-2 / immunology
  • Receptor, ErbB-2 / metabolism*
  • Trastuzumab

Substances

  • Antibodies, Monoclonal, Humanized
  • ERBB2 protein, human
  • Receptor, ErbB-2
  • Trastuzumab