Abstract 156P
Background
HER2 low (IHC 2+/ISH- or IHC 1+) breast cancer (BC) is an emerging subtype of BC with new therapeutic options in the metastatic setting. 45 to 55% of BC express low levels of HER2 which includes 37% of TNBC. In the early setting, little data have been reported on the impact of HER2 low expression on response to chemotherapy. This study investigates the link of HER2 status (HER2-0 versus low) and histological response after neoadjuvant chemotherapy in patients with early TNBC.
Methods
We retrieved retrospectively clinical and anatomopathological data from consecutive patients treated for an early unilateral TNBC between 2005 and 2020 at ICO. The primary endpoint was pCR (i.e., ypT0 ypN0), according to the HER2 status. Secondary endpoints included invasive disease free survival (iDFS) and overall survival (OS). Time-to-event endpoints were analyzed by using the log rank test.
Results
Out of the 449 TNBC patients included, 126 had a HER2-low tumor (95 HER2 1+, 31 HER2 2+). The median age was 51 years. Non-specific invasive carcinomas was predominant (94.7%), 93.3% were ≥ T2 (56% T2; 25% T3; 13% T4) and 57.1 % had node axillary involvement (48.2% N1, 9.9% N2, 1.5% N3). 75.7% had a SBR grade III tumors. Ki67 was significantly higher in the HER2-low group with a mean of 60.9% versus 49.0% in the HER2-0 group (p=0.008). The pCR rate was not significantly different between HER2-low group versus HER2-0 group (35.7 % versus 41.8 %, p=0.284) in univariable analysis even in multivariable analysis adjusted for TNM classification and grade (Odds ratio = 0.70, confidence interval 95% 0.45-1.08). With a median follow-up of 73.4 months [95% confidence interval: 70.28; 78.22], no association with iDFS nor OS was found between groups: 5-years iDFS (61.3% vs 70.3%; p=0.48) and 5-years OS (65.3% and 72.6% (p=0.329) the HER2-low and HER2-0 groups respectively.
Conclusions
In our cohort, the HER2 status was not significantly associated with pCR. However, the prognostic and predictive impact of HER2 low expression among TNBC warrants further evaluations.
Clinical trial identification
Editorial acknowledgement
Legal entity responsible for the study
The authors.
Funding
Has not received any funding.
Disclosure
J. Frenel: Other, Invited Speaker, consulting public presentation: Roche; Other, Invited Speaker, consulting public presentation: Novartis; Financial Interests, Invited Speaker, consulting public presentation: Lilly; Other, Invited Speaker, consulting public presentation: AstraZeneca; Other, Invited Speaker, consulting public presentation: Pfizer; Financial Interests, Invited Speaker, consulting public presentation: Bio cad; Financial Interests, Invited Speaker, consulting public presentation: Daiichi Sankyo; Financial Interests, Invited Speaker, consulting public presentation: GSK; Financial Interests, Invited Speaker, consulting public presentation: Pierre Fabre; Financial Interests, Invited Speaker, consulting public presentation: Amgen. P. Augereau: Financial Interests, Personal, Invited Speaker: AstraZeneca; Financial Interests, Personal, Invited Speaker: Novartis; Financial Interests, Personal, Invited Speaker: Pfizer; Financial Interests, Personal, Invited Speaker: Lilly. M. Campone: Financial Interests, Institutional, Advisory Role, Consulting/advisory/fees to the Institution: AstraZeneca; Financial Interests, Institutional, Advisory Role, Consulting/advisory/fees to the Institution: Sanofi; Financial Interests, Institutional, Advisory Role, Consulting/advisory/fees to the Institution: Servier; Financial Interests, Institutional, Advisory Role, Consulting/advisory/fees to the Institution: AbbVie; Financial Interests, Personal, Advisory Role, Consulting/advisory/honoraria: Lilly; Financial Interests, Institutional, Advisory Role, Consulting/advisory/fees to the Institution: Accord; Financial Interests, Personal, Speaker’s Bureau: Novartis; Financial Interests, Institutional, Advisory Role, Consulting/advisory/fees to the Institution: Pfizer; Financial Interests, Personal, Advisory Role: GT1; Financial Interests, Institutional, Advisory Role, Consulting/advisory/fees to the Institution: Seagen; Financial Interests, Personal, Advisory Role: Daiichi Sankyo. A. Patsouris: Financial Interests, Other: Lilly; Financial Interests, Other: Daiichi Sankyo; Non-Financial Interests, Other: Roche; Non-Financial Interests, Other: Pfizer; Non-Financial Interests, Other: Eisai; Non-Financial Interests, Other: Mundipharma. All other authors have declared no conflicts of interest.