258P - Correlation between pathological complete response (pCR) following neoadjuvant docetaxel, carboplatin and trastuzumab (TCH) with or without pertuzumab (TCHP) and PAM50 subtypes in HER2(+) early breast cancer (eBC)

Background

Addition of pertuzumab to trastuzumab based neoadjuvant regimens improves pCR in HER2(+) eBC. We seek to de-escalate pertuzumab in HER2 enriched (HER2E) eBC.

Methods

HER2(+) stage II-III BC patients (pts) treated with TCH or TCHP between 2010-23 were compiled retrospectively. Tumors RNA underwent BC360® assay. Aim= to assess correlation between pCR and neoadjuvant regimen in HER2E subtype. Event free survival (EFS) was analyzed. A subanalysis focusing on adjuvant trastuzumab monotherapy was conducted.

Results

248 out of 339 ITT pts had a BC360® assay. HER2E pts (median T=35 mm, ER 60%, N(+) 61%, stage III 30%). pCR rate for HER2E subtype was 72% compared to 36% for non-HER2E subtypes (p

Conclusions

Adding pertuzumab to neoadjuvant TCH does not significantly correlate with pCR in HER2E. Despite this lack of pCR improvement HER2E pts treated with TCHP showed better EFS irrespective of pathological response. EFS pertuzumab benefit was only observed in stage III or N(+) HER2E pts. These findings suggest a potential for de-escalating neoadjuvant pertuzumab in stage II or N(-) HER2E disease and warrant prospective validation.

Clinical trial identification

Editorial acknowledgement

Legal entity responsible for the study

Instituto de Investigación Sanitaria Gregorio Marañón, CiberOnc, Madrid, Spain.

Funding

Instituto de Investigación Sanitaria Gregorio Marañón, CiberOnc, Madrid, Spain.

Disclosure

C. Bueno Muiño: Financial Interests, Personal, Invited Speaker: Novartis, Daiichi Sankyo, AstraZeneca, GSK, Lilly; Financial Interests, Personal, Advisory Board: Pfizer. I. Echavarria Diaz-Guardamino: Financial Interests, Personal, Invited Speaker: Pfizer, Novartis, AstraZeneca, Pierre Fabre, Lilly, Gilead; Financial Interests, Personal, Advisory Board: Daichi Sankyo, Lilly. Y. Jerez Gilarranz: Financial Interests, Personal, Invited Speaker: Daichii, Novartis, roche, pfizer. B. Herrero Lopez: Financial Interests, Personal, Invited Speaker: Roche, Novartis, Pharmamar, Eisai, AstraZeneca, Daichii Sankyo, Pfizer, Teva, Kiowa Kirin, GSK, Gilead. T. Massarrah: Financial Interests, Personal, Advisory Board: GSK, NOVARTIS. P.D.L.M. de la Morena Barrio: Financial Interests, Personal, Invited Speaker: Daiichi sankyo, GSK, clovis, Lilly. F. Ayala de la Pena: Financial Interests, Personal, Advisory Board: Seagen, Novartis; Financial Interests, Personal, Invited Speaker: Lilly, Gilead, Pfizer, Novartis; Financial Interests, Institutional, Funding: Daichii Sankyo; Non-Financial Interests, Member: Sociedad Española de Oncología Médica, American Society of Clinical Oncology; Other, Educational grants/Travel expenses: Novartis, Gilead, Daichii Sankyo, Pfizer, Roche. J. Á. García Saenz: Financial Interests, Personal, Advisory Board: Seagen, AstraZeneca, Daiichi Sankyo, Novartis, Gilead, Menarini; Financial Interests, Personal, Speaker’s Bureau: Celgene, Lilly, Eisai, MSD, Exact Science, Tecnofarma, Nolver (Adium), Asofarma, Roche; Financial Interests, Personal, Other, Travel support: Gilead, AstraZeneca, Daiichi Sankyo. F. Moreno Anton: Financial Interests, Personal, Advisory Board: AstraZeneca, Pfizer, Daiichi Sankyo, MSD, Gilead; Financial Interests, Institutional, Research Grant: pfizer. A. Rodriguez: Financial Interests, Personal, Advisory Board: Roche, Pfizer, Lilly, Novartis, Astrazeneca, Daichi Sankyo; Financial Interests, Institutional, Funding: Roche, Lilly, Pfizer, Zymmeworks, Bristol Myers, Novartis, Gilead, Astrazeneca. T. Quintanar Verduguez: Financial Interests, Personal, Advisory Board: pfizer; Financial Interests, Personal, Invited Speaker: MSD Oncology, Daichi, Lilly, Novartis; Financial Interests, Institutional, Local Pi, Pi Clinical Trial: AstraZeneca. D. Bañón: Financial Interests, Personal, Invited Speaker: Pfizer, Pierre Fabre, Amgen. S. Lopez-Tarruella Cobo: Financial Interests, Personal, Advisory Board: AstraZeneca, Daiichi Sankyo, Pfizer, Novartis, Lilly, Gilead, GSK, Roche, Pierre Fabre, Seagen, Menarini_Stemline, Gebro Pharma, Veracyte, MSD; Financial Interests, Personal, Invited Speaker: Lilly; Non-Financial Interests, Member of Board of Directors: Geicam, Seom. M. Martin Jimenez: Financial Interests, Personal, Advisory Board: Astrazeneca, Lilly, Roche/Genentech, Daiichi Sankyo, Menarinio-Stemline; Financial Interests, Personal, Invited Speaker: Pfizer, AstraZeneca, Lilly, Novartis, Roche/Genentech; Financial Interests, Institutional, Research Grant: Novartis, Roche, Puma; Non-Financial Interests, Member of Board of Directors: TRIO; Non-Financial Interests, Leadership Role: Geicam; Non-Financial Interests, Member: ASCO; Non-Financial Interests, Advisory Board: SEOM. All other authors have declared no conflicts of interest.