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. 2014 Oct 29:6:169-77.
doi: 10.2147/BCTT.S69416. eCollection 2014.

Assessment of HER2 testing patterns, HER2+ disease, and the utilization of HER2-directed therapy in early breast cancer

David D Stenehjem  1 , Minkyoung Yoo  2 , Sudhir K Unni  2 , Mukul Singhal  2 , Hillevi Bauer  2 , Kim Saverno  2 , Cheng Quah  3 , Anthony Masaquel  3 , Diana I Brixner  4
Affiliations

Assessment of HER2 testing patterns, HER2+ disease, and the utilization of HER2-directed therapy in early breast cancer

David D Stenehjem et al. Breast Cancer (Dove Med Press). .

Abstract

Context: Determining human epidermal growth factor receptor 2 (HER2) status is critical for the management of early-stage breast cancer (ESBC). An understanding of HER2 testing practices can provide insight into how test results influence the use of HER2-directed therapy.

Objective: To assess HER2 testing, HER2+ disease, and HER2-directed therapy in ESBC at the Huntsman Cancer Institute before and after the 2007 American Society of Clinical Oncology and College of American Pathologist (ASCO/CAP) guidelines on HER2 testing were published.

Methods: Patients were identified from an institutional tumor registry. HER2 testing patterns and results were examined using a chart review of pathology and clinical notes. Patient characteristics, HER2+ rate, and trastuzumab use were evaluated descriptively. Discordance rate with reflex testing (immunohistochemistry [IHC]2+ retested by fluorescence in situ hybridization [FISH]) was also evaluated.

Results: A total of 1,459 women were included (mean age: 57 years). The rate of HER2+ disease was 17% (number [N] =245). The discordance rate between IHC2+ and FISH was 10%. After the 2007 ASCO/CAP guidelines, fewer tumors were classified as IHC3+ (16% post- versus 21.9% pre-2007), more tumors were characterized as IHC2+ (26.4% post- versus 20.7% pre-2007), and the overall HER2+ rate was decreased (18.7% versus 21.9%), but this was not statistically significant (P=0.519). Most patients with HER2+ ESBC received HER2-targeted therapy (N=185).

Conclusion: The HER2+ rate was 17% and within the range of the reported rates in the literature. Reflex testing identified additional HER2+ tumors by approximately 10%, and should be considered a potential quality indicator. ASCO/CAP HER2 testing guidelines in 2007 appeared to impact the interpretation and classification of HER2+ tumors.

Keywords: FISH; HER2; HER2-targeted therapy; early-stage breast cancer; human epidermal growth factor receptor 2; immunohistochemistry.

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Figures

Figure 1
Figure 1
Patient flow, HER2 status, and HER2-directed therapy utilization. Abbreviations: ICD-O, International Classification of Diseases for Oncology; n, number; ICD, International Classification of Diseases; EDW, enterprise data warehouse; HER2, human epidermal growth factor receptor 2.
Figure 2
Figure 2
HER2 positivity by (A) age, (B) estrogen receptor/progesterone receptor, (C) grade, and (D) stage. Abbreviations: n, number; HER2, human epidermal growth factor receptor 2.
See this image and copyright information in PMC

References

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