Retrospective observational study of HER2 immunohistochemistry in borderline breast cancer patients undergoing neoadjuvant therapy, with an emphasis on Group 2 (HER2/CEP17 ratio ≥2.0, HER2 copy number <4.0 signals/cell) cases.

Rakha, Emad A, Miligy, Islam M, Quinn, Cecily M, Provenzano, Elena, Shaaban, Abeer M, Marchiò, Caterina, Toss, Michael S, Gallagy, Grace, Murray, Ciara, Walshe, Janice, Katayama, Ayaka, Eldib, Karim, Badr, Nahla, Tanchel, Bruce, Millican-Slater, Rebecca, Purdie, Colin, Purnell, Dave, Pinder, Sarah E, Ellis, Ian O and Lee, Andrew H S (2021) Retrospective observational study of HER2 immunohistochemistry in borderline breast cancer patients undergoing neoadjuvant therapy, with an emphasis on Group 2 (HER2/CEP17 ratio ≥2.0, HER2 copy number <4.0 signals/cell) cases. British journal of cancer. ISSN 1532-1827.

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Official URL: https://www.nature.com/articles/s41416-021-01351-8

Abstract

BACKGROUND

The ASCO/CAP guidance on HER2 testing in breast cancer (BC) has recently changed. Group 2 tumours with immunohistochemistry score 2+ and HER2/CEP17 ratio ≥2.0 and HER2 copy number <4.0 signals/cell were re-classified as HER2 negative. This study aims to examine the response of Group 2 tumours to neoadjuvant chemotherapy (NACT).

METHODS

749 BC cases were identified from 11 institutions. The association between HER2 groups and pathological complete response (pCR) was assessed.

RESULTS

54% of immunohistochemistry HER2 positive (score 3+) BCs showed pCR, compared to 19% of immunohistochemistry 2+ FISH amplified cases. 27% of Group 2 treated with HER2 targeted therapy achieved pCR, compared to 19 and 11% in the combined Groups 1 + 3 and Groups 4 + 5, respectively. No difference in pCR rates was identified between Group 2 and Group 1 or combined Groups 1 + 3. However, Group 2 response rate was higher than Groups 4 + 5 (p = 0.017).

CONCLUSION

No difference in pCR was detected in tumours with a HER2/CEP17 ratio ≥2.0 and a HER2 score 2+ by IHC when stratified by HER2 gene copy number. Our data suggest that ASCO/CAP HER2 Group 2 carcinomas should be evaluated further with respect to eligibility for HER2 targeted therapy.

Item Type: Article
Subjects: QZ Pathology. Oncology
Divisions: Clinical Support > Pathology
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Depositing User: Mrs Caroline Tranter
Date Deposited: 29 Mar 2021 10:41
Last Modified: 29 Mar 2021 10:41
URI: http://www.repository.uhblibrary.co.uk/id/eprint/4143

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