FINDER1 compared efficacy, tolerability and pharmacokinetics (PK) of three fulvestrant dose regimens in postmenopausal Japanese women with estrogen receptor (ER)-positive locally advanced/metastatic breast cancer recurring or progressing after prior endocrine therapy.

The primary end point of this randomised, multicentre, phase II study was objective response rate (ORR) and the secondary end points included time to progression (TTP), clinical benefit rate (CBR), PK profiles and tolerability. Postmenopausal women with ER-positive advanced breast cancer were randomised to 28-day cycles of fulvestrant approved dose (AD), loading dose (LD) or high dose (HD) until disease progression.

Hundred and forty-three patients (median age 61 years) received fulvestrant AD (n = 45), LD (n = 51) or HD (n = 47). ORR was similar across dose regimens: 11.1%, 17.6% and 10.6% for AD, LD and HD, respectively, with overlapping confidence intervals. TTP and CBR were also similar between groups (median TTP: 6.0, 7.5 and 6.0 months, respectively; CBR: 42.2%, 54.9% and 46.8% for AD, LD and HD, respectively). C(max) and area under the plasma concentration-time curve were dose proportional and PK steady state was reached earlier with LD and HD than with AD. All three doses were well tolerated, with a similar adverse-event profile and no emerging safety concerns.

Fulvestrant AD, LD and HD had similar efficacy and tolerability profiles in postmenopausal Japanese women with ER-positive advanced breast cancer.