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Gaudio M, Jacobs F, Benvenuti C, Saltalamacchia G, Gerosa R, De Sanctis R, Santoro A, Zambelli A. Unveiling the HER2-low phenomenon: exploring immunohistochemistry and gene expression to characterise HR-positive HER2-negative early breast cancer. Breast Cancer Res Treat 2024; 203:487-495. [PMID: 37923964 DOI: 10.1007/s10549-023-07151-3] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 07/18/2023] [Accepted: 09/29/2023] [Indexed: 11/06/2023]
Abstract
PURPOSE HER2-low breast cancer (BC) is a novel entity with relevant therapeutic implications, especially in hormone receptor (HR) positive BC. This study examines whether HER2 mRNA through the 21-gene assay, Oncotype DX (ODX), can refine the diagnosis of HER2-low and HER2-zero, obtained by immunohistochemistry (IHC). METHODS Between Jan 2021 and Jan 2023, 229 consecutive HR-positive HER2-negative early BC (T1-3 N0-1) have been characterised by IHC and ODX. HER2 status by IHC was either zero (IHC-0) or low (IHC-1 + and IHC-2 + /ISH-negative) while HER2-zero was further divided into HER2-null (IHC-0) and HER2-ultralow (IHC-1-10%). HER2 gene expression by ODX was negative if lower 10.7. RESULTS The distribution of HER2 IHC was as follows: 53.3% HER2-0, 29.25% HER2-1 + , and 17.5% HER2-2 + . The clinicopathological characteristics were similar in the three groups, with higher PgR-negative rate in HER2-zero (13.9% vs 3% vs 5%). The distribution of RS was homogeneous in the three groups with the median HER2 gene expression of 9.20 [IQR: 8.70-9.60]. HER2 gene expression gradually increased as the IHC score, with substantial overlap. After adjusting for confounders, HER2-1 + and HER2 2 + had a significant positive correlation between HER2 gene expression and IHC [OR 1.42, 95% CI 1.21 to 1.68, p < 0.001; OR 1.96, 95% CI 1.61 to 2.37, p < 0.001] compared to the HER2-zero group. HER2 gene expression did not differ between HER2-null and HER2-ultralow subgroups. CONCLUSION Due to the substantial overlap, the HER2 gene expression is unable to properly distinguish HER2-low and HER2-zero IHC whose accurate identification is critical in the context of HER2-negative BC.
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Affiliation(s)
- M Gaudio
- Department of Biomedical Sciences, Humanitas University, 20072, Pieve Emanuele, MI, Italy
- Medical Oncology and Hematology Unit, IRCCS Humanitas Research Hospital, 20089, Rozzano, MI, Italy
| | - F Jacobs
- Department of Biomedical Sciences, Humanitas University, 20072, Pieve Emanuele, MI, Italy
- Medical Oncology and Hematology Unit, IRCCS Humanitas Research Hospital, 20089, Rozzano, MI, Italy
| | - C Benvenuti
- Department of Biomedical Sciences, Humanitas University, 20072, Pieve Emanuele, MI, Italy
- Medical Oncology and Hematology Unit, IRCCS Humanitas Research Hospital, 20089, Rozzano, MI, Italy
| | - G Saltalamacchia
- Department of Biomedical Sciences, Humanitas University, 20072, Pieve Emanuele, MI, Italy
| | - R Gerosa
- Department of Biomedical Sciences, Humanitas University, 20072, Pieve Emanuele, MI, Italy
- Medical Oncology and Hematology Unit, IRCCS Humanitas Research Hospital, 20089, Rozzano, MI, Italy
| | - R De Sanctis
- Department of Biomedical Sciences, Humanitas University, 20072, Pieve Emanuele, MI, Italy.
- Medical Oncology and Hematology Unit, IRCCS Humanitas Research Hospital, 20089, Rozzano, MI, Italy.
| | - A Santoro
- Department of Biomedical Sciences, Humanitas University, 20072, Pieve Emanuele, MI, Italy
- Medical Oncology and Hematology Unit, IRCCS Humanitas Research Hospital, 20089, Rozzano, MI, Italy
| | - A Zambelli
- Department of Biomedical Sciences, Humanitas University, 20072, Pieve Emanuele, MI, Italy
- Medical Oncology and Hematology Unit, IRCCS Humanitas Research Hospital, 20089, Rozzano, MI, Italy
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