280MO - Progression free survival with endocrine therapy, before or after chemotherapy, in patients with hormone receptor-positive/HER2-negative metastatic breast cancer in a large multicenter national observational study

Background

For HR+/HER2– metastatic breast cancer (mBC), the use of frontline endocrine therapy (ET) before chemotherapy (CT) is recommended by international guidelines, except in case of visceral crisis, for which CT is advised. However, before routine use of Cyclin-Dependent Kinase 4/6 inhibitors, many patients (pts) were given CT as first therapeutic line (L1). We aimed to compare the progression free survival (PFS) under ET, depending on whether it was given before or after any CT.

Methods

All pts who initiated treatment for a newly diagnosed mBC between 2008 and 2014 in all 18 French Comprehensive Cancer Centers were included in the ESME (Epidemiological Strategy and Medical Economics) mBC database. ESME collects and centralizes retrospective real-world data. Primary endpoint of the present study was the evaluation of PFS under the first ET (PFS-ET1), depending on its position in relation to CT. PFS-ET1 was defined as time between the starting date of first ET and first disease progression or death. Secondary endpoint was PFS under the second ET (PFS-ET2).

Results

Out of 16702 pts in ESME mBC database, 6293 pts with HR+/HER2- mBC who received at least one ET as metastatic disease were included. Median age at mBC diagnosis was 62.0 years (95%CI 23-96). Median follow-up reached 44.7 months (mo). As L1, 3832 (60.9%) pts received ET without CT (ET first group (ET1G)), while 2461 (39.1%) received CT (CT first group (CT1G)), with 2024 (32.2%) receiving ET as maintenance treatment (ET-M) after CT. Pts in CT1G were younger (median age 57.0 vs. 66.0, p<0.001) and more likely to have visceral metastases (59.5% vs. 39.4%, p<0.001). Median PFS-ET1 was 12.4 mo in ET1G vs. 12.6 mo in CT1G (HR 0.96, [95% CI 0.90;1.01], log-rank p=0.13). 1668 pts received at least two ET: 1069 (64.1%) as second-line therapy (L2) after L1 ET (ET1G) and 599 (36.0%) (CT1G) after at least one CT, with 279 (16.7%) as ET-M after CT L2. Median PFS-ET2 was 5.8 mo for ET1G vs. 5.6 mo for CT1G (HR 1.07 [95% CI 0.96;1.19], log-rank p=0.20).

Conclusions

In this large series of HR+/HER2– mBC pts, there was no difference in PFS on ET if it was given before or after CT. This was true both for first- and second-line ET.

Clinical trial identification

Editorial acknowledgement

Legal entity responsible for the study

R&D UNICANCER.

Funding

Roche, Pfizer, AstraZeneca, MSD, Eisai and Daiichi Sankyo.

Disclosure

A. Mailliez: Honoraria (self): Pfizer; Travel/Accommodation/Expenses: AstraZeneca; Travel/Accommodation/Expenses: Pierre Fabre. F. Le Du: Advisory/Consultancy: Lilly; Advisory/Consultancy: SeaGen; Advisory/Consultancy, Travel/Accommodation/Expenses: Novartis; Advisory/Consultancy, Travel/Accommodation/Expenses: Pfizer; Travel/Accommodation/Expenses: AstraZeneca; Travel/Accommodation/Expenses: Eisai. J-S. Frenel: Advisory/Consultancy, Travel/Accommodation/Expenses: Roche; Advisory/Consultancy, Travel/Accommodation/Expenses: AstraZeneca; Advisory/Consultancy, Travel/Accommodation/Expenses: Lilly; Advisory/Consultancy, Travel/Accommodation/Expenses: Pfizer; Advisory/Consultancy: GSK; Advisory/Consultancy: Eisai; Advisory/Consultancy, Travel/Accommodation/Expenses: Novartis. T. Bachelot: Honoraria (self), Travel/Accommodation/Expenses: Roche; Honoraria (self), Research grant/Funding (institution), Travel/Accommodation/Expenses: Novartis; Honoraria (self), Research grant/Funding (institution), Travel/Accommodation/Expenses: AstraZeneca; Honoraria (self), Research grant/Funding (institution), Travel/Accommodation/Expenses: Pfizer; Honoraria (self): Seattle Genetics. All other authors have declared no conflicts of interest.