Multicenter observational study of fulvestrant 500 mg in postmenopausal Japanese women with ER positive advanced or recurrent breast cancer after prior endocrine treatment (SBCCSG29 study)

Aim/Background

Fulvesrant 500 mg has been the choice of endocrine therapy for advanced or recurrent breast cancer after prior endocrine treatment since Nov. 2011 in Japan. The purpose of this study is to clarify the effectiveness and safety of fulvestrant 500 mg in clinical setting.

Methods

This is a multicenter, prospective and retrospective, observational study.132 postmenopausal women (prospective 3, retrospective 129, median age 66, median 4 prior regimens) with locally advanced or metastatic breast cancer, who were treated with fulvestrant, were registered. Information about patients' medical record was retrospectively obtained from 9 hospitals (Saitama Breast Cancer Clinical Study Group: SBCCSG) at Saitama prefecture in Japan from October 2012 to April 2014.The primary end point was time to treatment failure (TTF).The secondary end points were overall survival (OS), Objective response rate (ORR), Clinical benefit rate (CBR) and adverse events (AE) (CTCAE ver.4). The choices of subsequent therapy after fulvestrant were also evaluated.

Results

The median TTF was 6.1 months. The median TTF for fulvestrant treatment as 1st + 2nd line therapy were 6.4 months, 3rd line and more were 5.9 months, respectively. Median OS was 28.5 months (the starting date was first day of fulvestrant). ORR was 12.9% and CBR was 45.5%. The most common AEs were injection site reactions (9.1%). Rates of grade 3 were only 2.3% (3/132). The number of patients who had treated subsequent therapy after fulvestrant were 55 (60%) in receiving chemotherapy and mTOR inhibitor (Chemo + mTOR), and 38 (40%) in receiving only non-fulvestrant endocrine therapy. This study revealed 41 .8% CBR with Chemo + mTOR after fulvestrant compared with 10.5% for endocrine therapy. The TTF with Chemo + mTOR after fulvestrant was 6.8 versus 2.7 months with endocrine therapy (HR = 0.43; 95% CI, 0.27-0.67; P = 0.0003).

Conclusions

Fulvestrant 500 mg was effective and safe treatment for advanced or recurrent breast cancer patients after prior endocrine treatment in clinical setting.

Clinical trial identification

UMIN 000009110 (University hospital Medical Information Network).

Disclosure

All authors have declared no conflicts of interest.