Abstract P3-02-07: Combined Chemo-endocrine Therapy Maybe a New Option for HR+/HER2− Advanced Breast Cancer: A Prospective, Single-center Clinical Study of Fulvestrant plus Oral Vinorelbine

Abstract Background Fulvestrant have demonstrated synergistic antitumor effect with chemotherapy regimen. This study evaluates the efficacy and safety of Fulvestrant with Vinorelbine in patients with hormone receptor positive (HR+)/human epidermal growth factor receptor-2-negative (HER2−) recurrent or metastatic breast cancer. Methods In this prospective, single-arm and investigator-initiated clinical study, patients with recurrent or metastatic HR+/HER2− breast cancer after the first line adjuvant endocrine therapy for > 1 year were eligible, in which the subjects of the first line was defined as the patients with recurrence and metastasis after adjuvant endocrine therapy for over 1 year and did not receive treatment for the recurrence and metastasis and the second-line defined as the patients who had disease progression after receiving first-line endocrine therapy or first-line chemotherapy). Patients were administered i.m. Fulvestrant 500mg (day 1 per cycle for 28 days) and oral Vinorelbine (60 mg/m2 on day 1, 8 and 15 of each cycle). The primary endpoint was progression-free survival (PFS). Secondary endpoints included overall survival (OS), objective response rate (ORR), disease control rate (DCR), duration of response (DoR), and safety. The Kaplan–Meier method and log-rank test were used to evaluate PFS and OS. Results Total 38 HR+/HER2- advanced breast cancer patients with median follow-up time (25.1 months) were enrolled in, and median PFS [9.86 months (95% CI: 7.2, 23.13)] were discovered. The median PFS of the first-line and the second-line treatment population were 20.73 months (95% CI: 9.82, NR) and 4.27 months (95% CI: 3.68, NR), respectively. The median OS of the intent-to-treat (ITT) and the first-line treatment population were not reached, and the OS of the second-line treatment was 28.2 months (95% CI: 11.5, NR). The ORR of the ITT population was 39.47% (95% CI: 23.93, 55.01). The ORR of the patients receiving first-line and second-line treatments were 44.44% (95% CI: 25.70, 63.19) and 27.27% (95% CI: 0.95, 53.59), respectively. The DCR of ITT population was 92.11% (95% CI: 83.54, 100.00)], and the median DoR was approximately 15.33 months (95% CI: 7.23, 22.54)]. In the safety analysis, most of the adverse events were grade of 1/2, and none of grade 4/5 adverse events were reported. Conclusion This is the first exploratory study of Fulvestrant with oral Vinorelbine regimen in the treatment of HR+/HER2− recurrent and metastatic breast cancer conducted worldwide. The combinative chemo-endocrine therapy was efficacious, safe and promising for patients with HR+/HER2− advanced breast cancer. Citation Format: Xue Wang, Jian Yue, Jiayu Wang, Pin Zhang, Fei Ma, Binghe Xu, Peng Yuan. Combined Chemo-endocrine Therapy Maybe a New Option for HR+/HER2− Advanced Breast Cancer: A Prospective, Single-center Clinical Study of Fulvestrant plus Oral Vinorelbine [abstract]. In: Proceedings of the 2022 San Antonio Breast Cancer Symposium; 2022 Dec 6-10; San Antonio, TX. Philadelphia (PA): AACR; Cancer Res 2023;83(5 Suppl):Abstract nr P3-02-07.