238MO - PROMENADE: PembROlizuMab for early triple negative ER-low breast caNcer, reAl worlD frEnch cohort

Background

KEYNOTE-522 (NCT03036488) study showed that adding pembrolizumab to a neoadjuvant chemotherapy (NAC) regimen for Triple-Negative Breast Cancer (TNBC), improve significantly pathological complete response (pCR) and 3-years PFS. As recommended by ESMO and ASCO/CAP guidelines the cut-off to define Estrogene Receptor negative (ER-) Breast cancer (BC) was ≤1% tumour cells for ER. Nonetheless, tumors with ER 1%-9% expression, called “ER-low”, are treated like TNBC in France but there is a lack of data concerning this population.

Methods

We conducted a retrospective real-life study in 12 comprehensive cancer centers across France. All patients receiving KEYNOTE-522 regimen since his availability until April 2023 were included. The primary objective was to report the pCR (ypT0/isN0 or RCB 0) rate in estrogen and/or progesterone receptor low (1-9%) HER2- subgroups of BC patients treated according to the KEYNOTE-522 regimen.

Results

We included 114 female patients. The median age was 49 years (26-80) and 64(57%) were premenopausal. Hundred and two (89%) of patients had a tumor size ≥T2 and 58 (51%) were lymph node-negative. Hundred and two (89%) patients had invasive carcinoma of no special type. Tumors had aggressive characteristics with 95 (86%) grade 3 and a median Ki67 of 70% (10-95). Fifty-seven (50%) patients had a HER2- low BC. Eighty-three patients (72%) completed the KEYNOTE 522 regimen without deviation. Surgery consisted of a mastectomy for 50 (44%) patients and a sentinel lymph node excision biopsy for 57 (50%) patients. Eighty-five (75%) patients had a pCR. For the 27 patients without treatment completion and the 4 with missing data, 22 (70%) had a pCR. With a median follow-up of 17(6-32) months, 4 patients already relapsed, including one in pCR.

Conclusions

Tumors with ER-low status have a high rate of pCR after KEYNOTE 522 regimen closer to TNBC than ER+ BC reported in KEYNOTE 756. Our results suggest that patients with ER-low.HER2- BC must be treated as TNBC to maximize pCR. We will confirm these data in a larger series.

Clinical trial identification

Editorial acknowledgement

Legal entity responsible for the study

Centre de Lutte Contre le Cancer François Baclesse.

Funding

Has not received any funding.

Disclosure

F. Cherifi: Financial Interests, Institutional, Research Funding: Novartis. M. Leheurteur: Financial Interests, Institutional, Invited Speaker: Seagen, Astrazeneca; Financial Interests, Institutional, Local PI: Gilead, Msd, Novartis, Gsk; Non-Financial Interests, Personal, Other, Invitation congres: Lilly, Msd, Daichi. C. Bailleux: Financial Interests, Personal, Advisory Board: Novartis, AstraZeneca; Financial Interests, Personal, Invited Speaker: Novartis, Lilly, Seagen, AstraZeneca; Financial Interests, Personal, Stocks/Shares, <1%: SigBio. J. Frenel: Financial Interests, Personal, Advisory Board: Pfizer, Novocure, Pierre Fabre, Eisai, Seagen, Gilead; Financial Interests, Personal, Invited Speaker: GSK, Amgen, Eisai; Financial Interests, Institutional, Advisory Board: Exactscience, lilly, Daiichi Sankyo, AstraZeneca, Clovis Oncology; Financial Interests, Institutional, Invited Speaker: Novartis, MSD; Financial Interests, Coordinating PI: AstraZeneca, Seagen; Financial Interests, Local PI: MSD, Daiichi Sankyo; Non-Financial Interests, Principal Investigator: Novartis, Lilly, AstraZeneca, Pfizer, Daiichi Sankyo, MSD. 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. 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. G. Emile: Financial Interests, Personal, Advisory Board: Novartis, AstraZeneca, Daiichi Sankyo, Seagen, Gilead; Financial Interests, Institutional, Local PI: Novartis, Roche, G1 Therapeutics, Lilly, Bayer, Celcuity, Seagen. All other authors have declared no conflicts of interest.