Manabu Futamura1*, Takumi Nakada2, Yoshinori Kawaguchi3, Masahito Nawa3, Makoto Takeuchi4, Kazuhiro Ishihara5, Yasuko Nagao6, Kasumi Morimitsu1, Atsuko Ogiso6, Toshihisa Matsuki7, Junko Kato5, Yoshimi Asano6, Yoshihisa Tokumaru1, Toshio Shimokawa8 and Kazuhiro Yoshida1
1Department of Breast Surgery, Gifu University, Japan
2Department of Breast Surgery, Gifu Municipal Hospital, Japan
3Department of Breast Surgery, Asahi University Hospital, Japan
4Department of Breast Surgery, Kizawa Memorial Hospital, Japan
5Department of Surgery, Gihoku Kosei Hospital, Japan
6Department of Breast Surgery, Gifu Prefectural General Medical Center, Japan
7Department of Surgery, Ibi Kosei Hospital, Japan
8Clinical Study Support Center, Wakayama Medical University, Japan
This multi-institutional prospective cohort study aimed to examine the efficacy and safety of 500 mg of Fulvestrant (Ful-500) in postmenopausal Estrogen Receptor (ER)-positive Advanced or Recurrent Metastatic Breast Cancer (AMBC). Patients with second, third or fourth-line Endocrine Therapy (ET) were recruited. From August 2013 to June 2016, participants were administered Ful500 as two 5-mL intramuscular injections on days 0, 14, and 28 and thereafter, every 28 days until disease progression. The primary endpoint was Progression-Free Survival (PFS). Overall Response Rate (ORR), Clinical Benefit Rate (CBR), and safety were the secondary endpoints. For PFS, the Kaplan-Meier method was used to estimate the survival curve with a threshold Median Survival Time (MST) of 3 months and an expected MST of 5.5 months, at a one-sided significance level of 0.05 and power of 0.8. All statistical tests were two-sided. A 5% error was used in the PFS analysis. Of the 51 enrolled patients, 46 (second-line: 31, third-line: 10, fourth-line: 5) were analyzed. The median PFS duration was 8.5 months (95% confidence interval [CI], [5.6-14.5]). Furthermore, the 90% CI of the mean PFS was 5.6-14.5 months. The lower 90% CI value was higher than the median PFS (3 months) threshold, signifying that Ful-500 use was effective in these patients. The ORR and CBR values were 6.5% (3/46) and 71.7% (33/46), respectively. Adverse events, all grades 1-2, were observed in 15 cases (32.6%). Ful-500 use was effective and safe in second to fourth-line ET for ER-positive postmenopausal AMBC.
Futamura M, Nakada T, Kawaguchi Y, Nawa M, Takeuchi M, Ishihara K, et al. Examination of the Efficacy of Fulvestrant 500 mg Targeting Estrogen Receptor-Positive Postmenopausal Metastatic Breast Cancer: Prospective Observational Study (PerSeUS BC03 Study). Clin Oncol. 2019; 4: 1633 .