Everolimus (EVE) plus endocrine therapy in patients with estrogen receptor–positive (ER+), human epidermal growth factor receptor 2–negative (HER2−) advanced breast cancer (BC): First- and second-line data from the BOLERO-4 study.

Abstract

1010 Background: Initial first-line (1L) data from the phase 2 BOLERO-4 (NCT01698918) study of EVE + letrozole (LET) in postmenopausal patients (pts) with ER+, HER2− metastatic BC (MBC) or locally advanced BC (LABC) have been previously reported. Here, we present updated 1L progression-free survival (PFS) data, plus new data describing second-line (2L) EVE + exemestane (EXE) in pts with disease progression after EVE + LET. Methods: Postmenopausal pts with ER+, HER2− MBC or LABC with no prior therapy for advanced disease received EVE 10 mg/day + LET 2.5 mg/day. After disease progression, pts could receive EVE + EXE 25 mg/day until further disease progression, unacceptable toxicity, or withdrawal of consent. Primary endpoint: 1L PFS. Secondary endpoints: overall response rate (ORR), clinical benefit rate (CBR), 2L PFS, overall survival (OS), and safety (1L and 2L). Results: Among 202 pts (median age, 64 years) with 1L MBC (96%) or LABC (4%), median PFS (95% CI) was 21.7 (18.1–23.9) months, ORR was 43.6%, and CBR was 74.3%. 42 pts (median age, 62 years) with MBC (88%) or LABC (12%) who progressed on 1L EVE + LET received optional 2L EVE + EXE. 2L median PFS (95% CI) was 3.7 (1.8–9.1) months, ORR was 4.8%, and CBR was 21.4%. Common 1L adverse events (all grades, regardless of drug relationship) were stomatitis (69%), weight loss (44%), diarrhea (40%), nausea (37%), and anemia (35%); 2L adverse events included stomatitis (19%) and weight loss (19%). Median duration of follow-up from start of 1L to the data cutoff for these new analyses (17 June 2016) was 23.5 months. OS will be analyzed at a later data cut. Conclusions: EVE + LET is an effective regimen in 1L ER+, HER2− advanced BC. Thesedata support previously reported BOLERO-2 data demonstrating a PFS improvement from addition of EVE to an aromatase inhibitor. 2L data, although limited by the small number of pts, show preliminary evidence of EVE activity when continued beyond disease progression. No new safety signals were seen. Lower rates of stomatitis in 2L were noted. Clinical trial information: NCT01698918.