Abstract 291P
Background
HER2-low (i.e. HER2 IHC 1+ or 2+ in the absence of HER2 gene amplification) breast cancer (BC) is a new entity, with emerging dedicated treatments. Few data have been reported on this specific subtype. Based on a national database, we aimed at evaluating the prognosis of pts with HER2 low MBC in a real-world setting.
Methods
The ESME metastatic breast cancer platform (NCT03275311) is a retrospective real-life database using a clinical trial-like methodology to collect data from 18 French Comprehensive Cancer Centers. It includes data from each newly diagnosed MBC patient (pt) having initiated at least one treatment between 2008 and 2016 in one of the participating centers. HER2-low BC cases were compared to the overall HER2 score 0 population, regarding first-line progression free survival (PFS1) and overall survival (OS).
Results
Of the 15054 HER2 “negative” MBC in the database, 4671 (31%) and 10383 (69%) pts had HER2-low and HER2 0 MBC respectively. Most of the HER2-low MBC (N=4,083, 87.4%) were HR+, while 588 (12.6%) were triple negative. Median age was 61y (22-103); tumor grade was mainly 1/2 (68.8%). Metastatic disease was de novo in 37.3% of pts which was significantly higher than HER2 0 MBC pts (27.8%, p<0.0001). With a median follow up of 49.5m (48.6-50.4), median OS of the HER2-low cohort was 38m (36.4-40.5) compared to 33.9m [32.9-34.9] for pts with HER2 0 tumors (p<0.0001). After adjustment on age, presence of visceral metastases, number of metastatic sites, de novo disease, period of care and HR status, HER2-low patients had a better OS (HR adjusted=0.95; CI 95% [0.91-0.99], p=0.024) compared to HER2 0 patients. Details according to HR status are presented below. HER2-low status was not associated with differential PFS1 in the whole population (adjusted HR=0.99; CI 95% [0.95-1.02] p=0.45). Table: 291P
| Subtype | N | OS median | Adjusted HR | p-value | |
| HR+ | HER2 0 | 8,188 | 41.8 [40.5-42.8] | 1 | |
| HER2-low | 4,083 | 43.0 [41.5-44.4] | 0.96 [0.92-1.02] | 0.173 | |
| Triple-negative | HER2 0 | 2,195 | 13.3 [12.6-14.0] | 1 | |
| HER2 0 | 588 | 15.6 [13.5-17.4] | 0.91 [0.82-1.01] | 0.093 |
Conclusions
This is is the largest study of HER2-low MBC patients to date in a real world setting. HER2-low MBC may have a disctinct outcome from HER2 0 MBC. Dedicated clinical trials are ongoing.
Clinical trial identification
Editorial acknowledgement
Legal entity responsible for the study
J-S. Frenel.
Funding
Roche, Pfizer, AstraZeneca, Eisai, Daiichi Sankyo, MSD.
Disclosure
J. Frenel: Financial Interests, Personal, Invited Speaker: Roche; Financial Interests, Personal, Advisory Board: Novartis; Financial Interests, Personal, Advisory Board: Lilly; Financial Interests, Personal, Advisory Board: Pfizer; Financial Interests, Personal, Advisory Board: Daiichi Sankyo; Financial Interests, Personal, Advisory Board: AstraZeneca; Financial Interests, Personal, Invited Speaker: GSK; Financial Interests, Personal, Advisory Board: Novocure; Financial Interests, Personal, Invited Speaker: Amgen; Financial Interests, Personal, Invited Speaker: MSD; Financial Interests, Personal, Advisory Board: Pierre Fabre; Non-Financial Interests, Principal Investigator: Roche; Non-Financial Interests, Principal Investigator: Novartis; Non-Financial Interests, Principal Investigator: Lilly; Non-Financial Interests, Principal Investigator: AstraZeneca; Non-Financial Interests, Principal Investigator: Pfizer; Non-Financial Interests, Principal Investigator: Daiichi Sankyo; Non-Financial Interests, Principal Investigator: MSD. T. Bachelot: Non-Financial Interests, Personal, Advisory Board: Roche; Financial Interests, Personal, Advisory Board: AstraZeneca; Financial Interests, Personal, Advisory Board: Pfizer; Financial Interests, Personal, Advisory Board: Seattle Genetics; Financial Interests, Personal, Advisory Board: Novartis. V.C. Dieras: Financial Interests, Personal, Advisory Board: Roche; Financial Interests, Personal, Advisory Board: Novartis; Financial Interests, Personal, Advisory Board: Lilly; Financial Interests, Personal, Advisory Board: Pfizer; Financial Interests, Personal, Advisory Board: AstraZeneca; Financial Interests, Personal, Advisory Board: Eisai; Financial Interests, Personal, Advisory Board: AbbVie; Financial Interests, Personal, Advisory Board: MSD; Financial Interests, Personal, Advisory Board: Seattle Genetics; Financial Interests, Personal, Advisory Board: Daiichi Sankyo. T. Petit: Financial Interests, Personal, Advisory Board: Novartis; Financial Interests, Personal, Advisory Board: Lilly; Financial Interests, Personal, Advisory Board: Pfizer; Financial Interests, Personal, Advisory Board: Mylan; Financial Interests, Personal, Advisory Board: Daiichi Sankyo; Financial Interests, Personal, Advisory Board: Pierre Fabre. S. Delaloge: Financial Interests, Institutional, Invited Speaker: AZ; Financial Interests, Institutional, Advisory Board: AZ; Financial Interests, Institutional, Advisory Board: Cellectis; Financial Interests, Institutional, Invited Speaker: Exact Science; Financial Interests, Institutional, Advisory Board: Isi Servier; Financial Interests, Institutional, Invited Speaker: Lilly; Financial Interests, Institutional, Invited Speaker: MSD; Financial Interests, Institutional, Advisory Board: Novartis; Financial Interests, Institutional, Advisory Board: Orion; Financial Interests, Institutional, Invited Speaker: Pfizer; Financial Interests, Institutional, Advisory Board: Pierre Fabre; Financial Interests, Institutional, Advisory Board: Rappta; Financial Interests, Institutional, Advisory Board: Sanofi; Financial Interests, Institutional, Invited Speaker: Seagen. All other authors have declared no conflicts of interest.