Abstract 2713
Background
Premenopausal women with MBC have a distinct tumor biology, and more aggressive behavior. In the BOLERO-2 trial, adding EVE to exemestane (EXE) significantly prolonged progression-free survival (PFS) compared with EXE alone in postmenopausal women with recurrent/metastatic HR+, HER2– breast cancer. LEO is the first randomized phase II trial investigating the effect of adding EVE to LET in ovarian suppressed premenopausal women with MBC.
Methods
Patients (pts) with progression or prior exposed to tamoxifen with or without GnRH agonist, either sequentially or concurrently, in adjuvant or metastatic setting were randomly assigned (2:1) to receive LEUP+LET+EVE (arm A) or LEUP+LET (arm B) until disease progression or unacceptable toxicity. Randomization was stratified by the presence of visceral metastases and sensitivity to endocrine therapy. The primary end point was PFS. Secondary end points included overall survival (OS), objective response rate (ORR), and safety.
Results
Between January 2014 and October 2018, 137 pts were enrolled in this study. Baseline characteristics were well balanced between the two groups. The median age was 44 years (range 24-54), 74.5% had endocrine-sensitive disease, and 60.6% had visceral metastasis. At a median follow-up of 32.4 months, the median PFS was 18.1 months in arm A and 13.8 months in arm B, respectively (HR 0.73; 95% CI, 0.48 to 1.11; P = 0.137), and predominant in pts with visceral metastases (16.4 vs. 9.5 Mo) (HR 0.58; 95% CI, 0.34 to 0.99; p = 0.048). The median OS was not reached in both arms. ORR was 46.9% and 28.2% in arms A and B, respectively (P = 0.051). The most common grade 3/4 adverse events were neutropenia (9.8% in arm A vs. 0% in arm B), AST elevation (5.4% vs. 0%), enterocolitis (4.3% vs. 0%), and anemia (3.3% vs. 0%), without grade 3/4 stomatitis in both arms. Five pts discontinued treatment (1 AKI, 1 pneumonitis, 1 liver dysfunction, 2 unknown) but no treatment related death.
Conclusions
Adding EVE to LET demonstrated numerically improved PFS (D 4.3 Mo, median PFS), higher ORR. Significant improved PFS was noted in patients with visceral metastases.
Clinical trial identification
NCT02344550.
Editorial acknowledgement
Legal entity responsible for the study
Sung-Bae Kim.
Funding
Novartis, Dongkook Pharma Co. Ltd.
Disclosure
All authors have declared no conflicts of interest.
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