Dual targeting of HER2-positive breast cancer with trastuzumab emtansine and pertuzumab: understanding clinical trial results

Alberto Ocaña _, Eitan Amir and Atanasio Pandiella

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Oncotarget. 2018; 9:31915-31919. https://doi.org/10.18632/oncotarget.25739

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Alberto Ocaña1, Eitan Amir2 and Atanasio Pandiella3

1Translational Research Unit, Albacete University Hospital, and CIBERONC, Albacete, Spain

2Division of Medical Oncology and Hematology, Princess Margaret Cancer Centre, University of Toronto, Toronto, Canada

3Cancer Research Center, CSIC-IBSAL and CIBERONC, Salamanca, Spain

Correspondence to:

Alberto Ocaña, email: [email protected]

Keywords: breast cancer; HER2; trastuzumab; pertuzumab; TDM1

Received: May 15, 2018     Accepted: June 23, 2018     Published: August 07, 2018


Targeting of HER2-positive tumors with trastuzumab has shown to improve survival in early stage and advanced breast cancer. The addition of pertuzumab, another anti-HER2 antibody, to trastuzumab-containing regimens has demonstrated a modest increase in disease-free survival in the adjuvant setting. Unexpectedly, when pertuzumab was explored in combination with the antibody-drug conjugate TDM1 in the metastatic setting, no additional benefit was observed compared with dual targeting of HER2 with pertuzumab and trastuzumab, together with chemotherapy. Similar results were observed when exploring pathologic complete response in the neoadjuvant setting. In this article, we discuss basic science and translational data that may explain the limited efficacy observed with the combination of TDM1 and pertuzumab, including tumor heterogeneity, clonal selection, bystander effect or downregulation of the receptor by competitive binding. In addition, we review ongoing studies that could help to understand these findings.

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