Abstract 235P
Background
Fulvestrant and exemestane are both standard of care for estrogen receptor (ER) positive locally advanced or metastatic breast cancer. It is still controversial which drug is the optimal first-line endocrine monotherapy for postmenopausal ER+/HER2- breast cancer who exposed to adjuvant nonsteroidal aromatase inhibitors (NSAIs).
Methods
In this randomized, open-label, multi-center, parallel-group study, postmenopausal women with recurrent ER+/HER2- advanced breast cancer receiving at least 2 years NSAIs as adjuvant treatment were randomly assigned to receive fulvestrant (500 mg on days 0, 14, and 28 and every 28 (± 3) days thereafter) or exemestane (25 mg daily).
Results
A total of 144 patients were randomly assigned to receive fulvestrant(n=77) or exemestane(n=67). The median progression-free survival (PFS) was 8.51 months in fulvestrant group versus 5.55 months in exemestane group (P = 0.014, HR=0.615, 95%Cl: 0.417∼0.907). The ORR of the fulvestrant group was 19.48% compared to 5.97% of the exemestane group (P =0.017). Time to failure (TTF) was significantly longer for fulvestrant versus exemestane (median TTF was 8.38 months in the fulvestrant group and 5.45 months in the exemestane group, P=0.008). No significant differences in the incidence of adverse events and severe adverse events between the two groups. As an exploratory outcome, there were 22 patients with ESR1 mutation in 139 patients (15.8%). PFS had no significant differences for fulvestrant vs exemestane therapies in ESR1 mutation (P = 0.058) or wild-type patients (P = 0.087).
Conclusions
Fulvestrant 500 mg was associated with a statistically significant increase in PFS compared with exemestane and was generally well tolerated. There were no significant differences in PFS between the two groups irrespective of ESR1 status.
Clinical trial identification
NCT02646735.
Editorial acknowledgement
Legal entity responsible for the study
Beijing Association of Breast Diseases Prevention and Treatment.
Funding
AstraZeneca China.
Disclosure
All authors have declared no conflicts of interest.