263P - Association between clinicopathological characteristics and pathological complete response in patients with triple negative breast cancer treated by neoadjuvant chemo-immunotherapy

Background

Pathological complete response (pCR) following neoadjuvant chemo-immunotherapy (NACi) is associated with improved patient outcomes in early triple-negative breast cancer (TNBC). In this study, we aimed to determine clinical and pathological biomarkers associated with pCR after NACi in a prospective real-life cohort of patients treated at Institut Curie hospitals.

Methods

All patients who received NACi (pembrolizumab + carboplatin/paclitaxel followed by doxorubicin/cyclophosphamide) and underwent surgery for early-stage II-III TNBC (ER/PR expressed in <10% of tumour cells) at Institut Curie hospitals, France (Paris and Saint-Cloud) between August 2021 and June 2023 were included in this study.

Results

Two hundred and six patients with stage II-III TNBC, of whom N=29 (14%) had a low expression (1-9%) of ER, were evaluable for pCR. Overall pCR rate was 70% (N=144/206), and pCR rate was not statistically different between ER<1% (N=122/177, 69%) and ER-low (N=22/29, 76%, OR=1.42, 95%CI [0.6-3.76]) tumours. Factors associated with pCR rates were tumour size (cT1-2 vs cT3-4 OR=2.62 [1.35-5.06]), Ki-67≥30% (OR=8.0 [3.09-23.4]), germline mutation in homologous recombination (HR) genes (OR= 7.5 [2.2-47.5]) and PD-L1 CPS score (OR=1.03 [1.01-1.06]). The absence of ductal carcinoma in situ (DCIS) on the pre-treatment biopsy before surgery was associated with a higher pCR rate (OR=2.86 [1.34-6.11]). Although lobular and apocrine carcinomas were rare, we did not observe pCR in these histological subtypes (N=0/3 and N=0/4, respectively). In a multivariate model, Ki-67≥30% (HR 9.85 [2.93-40.7]), CPS (>20 vs 0-20 OR=3.44 [1.15-12.8]), absence of DCIS at initial biopsy (OR=2.55 [1.08-6.05]) and germline mutations of HR genes (OR=6.72 [1.67-47.7]) remained strong independent predictors of pCR after NACi.

Conclusions

Capitalizing on a large real-life cohort of patients with early TNBC, we report that a germline mutation in HR genes, Ki-67≥30%, histological type and absence of DCIS on pre-treatment biopsy are predictive of a pCR in stage II-III TNBC undergoing NACi. Importantly, low ER expression was not associated with a lower pCR to NACi.

Clinical trial identification

Editorial acknowledgement

Legal entity responsible for the study

Institut Curie.

Funding

Has not received any funding.

Disclosure

A. Vincent-Salomon: Financial Interests, Personal, Invited Speaker, Lectures honorarium: AstraZeneca; Financial Interests, Personal, Advisory Board: Daiichi Sankyo, Ibex, Roche, PRIMAA; Financial Interests, Personal, Invited Speaker: MSD, Roche; Financial Interests, Personal, Stocks/Shares: Ibex; Financial Interests, Institutional, Research Grant: AstraZeneca, Ibex; Financial Interests, Institutional, Funding: Owkin; Financial Interests, Institutional, Research Grant, MSD Avenir research grant: MSD; Non-Financial Interests, Member of Board of Directors: RUBAN ROSE association. I. Bieche: Financial Interests, Personal, Invited Speaker, 2 hours: AstraZeneca. D. Bello Roufai: Financial Interests, Personal, Advisory Board: MSD, Lilly, AstraZeneca, Gilead. F.C. Bidard: Financial Interests, Personal, Advisory Board: Pfizer, Lilly, Novartis, AstraZeneca, GE Healthcare, SAGA Diagnostics, Daiichi Sankyo, Gilead, Inatherys; Financial Interests, Personal, Invited Speaker: AstraZeneca, Pfizer, Seagen, Daiichi Sankyo; Financial Interests, Institutional, Research Grant: Pfizer, Merck KGaA, Roche; Financial Interests, Institutional, Funding: Prolynx, Saga Diagnostics, Merck KGaA; Financial Interests, Institutional, Steering Committee Member: AstraZeneca, Lilly, Pfizer; Financial Interests, Personal and Institutional, Steering Committee Member: Lilly. D. Loirat: Financial Interests, Personal, Advisory Board: MSD, AstraZeneca, Pfizer, Novartis, ExactSciences; Financial Interests, Personal, Other, Travel/congress: MSD; Financial Interests, Personal, Other, Travel/Congress: ROCHE, AstraZeneca, Gilead, Novartis; Financial Interests, Personal, Invited Speaker: Gilead, Lilly; Financial Interests, Personal, Other, Travel/Congres: Pflizer. E. Romano: Financial Interests, Personal, Advisory Board: Roche; Financial Interests, Institutional, Research Grant, Research fundings: BMS, AstraZeneca, Amgen, Janssen, Replimune; Financial Interests, Coordinating PI: Light Chain Biosciences; Non-Financial Interests, Principal Investigator: Dragofly Therapeutics, BMS, Roche, MSD/MERCK, ImCheck Therapeutics, AstraZeneca, Pfizer. All other authors have declared no conflicts of interest.