Real-world effectiveness and safety with sacituzumab govitecan (SG)–based therapy in metastatic breast cancer (MBC) in China: A multicenter retrospective study.

e13181 Background: SG was approved to treat patients who have received ≥1 prior systemic therapy in metastatic setting with triple-negative (TN) MBC or prior endocrine therapy including CDK4/6 inhibitor and chemotherapy with hormone receptor-positive (HoR+) MBC. Little real-world evidence is available in China. This study aimed to describe treatment patterns, clinical outcomes and safety profile for SG-based therapy and explore the predictors of effectiveness in Chinese women with MBC in real-world practice. Methods: MBC patients treated with SG (10 mg/kg D1, D8, every 21 days) between June 2023 and December 2024 in 3 institutions nationwide were included in this study. Clinical outcomes included real-world progression-free survival (PFS), overall survival (OS), objective response rate (ORR) and clinical benefit rate (CBR). Adverse event (AE) was evaluated according to the NCI-CTC version 5.0. Results: A total of 165 patients were enrolled, with 103 (62.4%) TN and 62 (37.6%) HoR+HER2-. Among TNBC and HoR+HER2- patients, median age was 51 and 58 years, 10.7% and 12.7% ECOG scores of 2, 72.8% and 85.5% of patients with visceral metastases, 13.6% and 16.1% of patients with brain metastasis, median prior lines in metastatic setting were 2 and 3, respectively. The majority of patients were treated with SG monotherapy, and a small number received SG-based combination therapy. At the cutoff date of 21 Jan 2025, in TNBC patients, median rwPFS was 5.1 mo (95%CI 3.8-7.4), median rwOS was 19.7 mo (95%CI 17.3-NR), ORR was 17.5% and DCR was 47.6%; in HoR+HER2- patients, median rwPFS was 5.8 mo (95%CI 4.7-7.9), the OS data were immature, ORR was 9.7% and DCR was 40.3%. Prior PD-1/PD-L1 inhibitors exposure (3.6 vs 7.8 mo, HR = 1.91, P = 0.025) and liver metastasis (5.5 vs 7.9 mo, HR = 2.96, P = 0.021) showed significantly shorter rwPFS in TNBC and HoR+HER2- patients in multivariate analysis, respectively. Longer rwPFS was observed in patients receiving SG as front line (line 1-2) compared to those as later line (line ≥3) both in TNBC ( P = 0.017) and HoR+HER2- patients ( P = 0.652). SG-based combination therapy showed a trend to improved PFS compared to monotherapy both in TNBC (14.2 vs 4.6 mo, HR = 0.51, P = 0.115) and HoR+HER2- patients (11.3 vs 5.8 mo, HR = 0.35, P = 0.159). Brain metastasis and prior use of ADCs did not impact the effectiveness of SG. Incidence of AEs of any grade was 52.7% and grade ≥3 AEs was 20.0%. No new safety signal was observed in this study. 14 (8.5%) patients discontinued the treatment and 15 (9.1%) had dose reduction due to AEs. Conclusions: In the real-world practice, SG showed anti-tumor activity in heavily pretreated Chinese MBC patients, consistent with existing clinical trials. mTNBC patients with no prior PD-1/PD-L1 exposure had longer rwPFS. Promising PFS of SG-based combination therapy encourages randomized controlled trials in the future. Clinical trial information: NCT06356519 .