Number of Patients Screened	58
Number of Patients Enrolled	58
Number of Patients Evaluable for Toxicity	58
Number of Patients Evaluated for Efficacy	58
Evaluation Method	RECIST 1.1
Response Assessment CR	n = 0 (0%)
Response Assessment PR	n = 8 (14%)
Response Assessment SD	n = 41 (70%)
Response Assessment PD	n = 9 (16%)
Response Assessment OTHER	n = 0 (0%)
(Median) Duration Assessments PFS	16.1 months, CI: 10.3–21.0
Outcome Notes
During the first stage, 17 of the first 24 patients (71%; 95% CI, 49%–87%) experienced a clinical benefit, thus meeting the threshold for continuing enrolment. Overall, the CBR and ORR were 76% (95% CI, 63%–86%) and 14% (95% CI, 6%–25%), respectively. Of the 58 patients' best response, 8 (14%) achieved partial response, 19 (33%) had stable disease, and 22 (38%) neither achieved complete response nor had disease progression. Progressive disease was observed in nine patients (16%). In the investigator‐based assessment, 35 patients still had measurable disease after first‐line chemotherapy, of whom 8 (23%) had a partial response and 19 (54%) had stable disease as best response. The CBR among measurable patients was 69% (95% CI, 51%–83%), and the ORR was 23% (95% CI, 10%–40%). By the data cutoff date, the median follow‐up was 32.6 months. No patients died during fulvestrant treatment. The median PFS since commencing fulvestrant maintenance therapy was 16.1 months (95% CI, 10.3–21.0 months; Fig. 1), with 1‐ and 2‐year PFS rates of 60% (95% CI, 46%–71%) and 35% (95% CI, 23%–47%), respectively. Twenty‐three deaths had occurred at the time of data cutoff. The median duration of OS had not been reached at the time of data analysis. The rate of OS at 3 years was 51% (95% CI, 32%–67%).