393P Real-world (RW) use patterns, effectiveness, and tolerability of sacituzumab govitecan (SG) for second-line (2L) and later treatment of metastatic triple-negative breast cancer (mTNBC)

SG is a Trop-2-directed antibody-drug conjugate approved in multiple countries for patients (pts) with mTNBC after ≥ 2 prior systemic therapies (≥ 1 for metastatic disease). In the ASCENT study (NCT02574455) in pts with mTNBC, SG had superior efficacy vs single-agent chemotherapy and a manageable safety profile (Bardia et al. NEJM 2021 ). This study describes RW SG dosing and clinical outcomes in pts with mTNBC treated with SG in 2L and later in the US. This retrospective cohort study used de-identified US electronic health records in the ConcertAI database of pts (≥ 18 y) with mTNBC treated with SG in 2L and later from April 2020 to May 2022 to allow for a 3-month minimum data accrual. Clinical outcomes (RW overall survival [rwOS], time to next treatment or death [TTNTD], and RW progression-free survival [rwPFS]) from start of SG (index date) were estimated by Kaplan-Meier methods. 230 female pts (median age 60 y, 26% Black, 17% ECOG performance status ≥ 2, 66% treated in community settings) were included in the analysis. Median follow-up was 7.2 months (IQR 3.9-11.1). SG RW outcomes for all pts and by SG line (2L and 3L+) are in the Table. Clinical outcomes were similar for all pts and stratified analyses (by race, concomitant G-CSF use, treatment-free interval duration). Of 134 pts (58%) who had G-CSF during SG treatment, 99 (74%) previously received G-CSF. Median time from SG start to G-CSF use was 8.5 days (IQR 8-29). SG was discontinued due to toxicity in 17 pts (7%).Table: 393P2L mTNBCSG n = 773L mTNBCSG n = 1532L+ mTNBCSGN = 230Median rwOS (95% CI), months*†13.9 (9.8-NE)8.4 (7.4-10.3)10.0 (8.3-11.1)rwOS rate (95% CI), %12-month51 (37-64)35 (26-44)40 (33-48)24-month32 (13-54)20 (11-29)23 (15-32)Median TTNTD (95% CI), months†4.8 (3.2-6.9)4.4 (3.8-5.5)4.6 (3.9-5.3)Median rwPFS (95% CI), months†4.9 (2.9-6.0)3.5 (2.7-4.2)3.8 (3.1-4.3)IQR, interquartile range; NE, not estimable. *Kalinsky et al. ASCO 2023 abstr e18879. †Measured from index date. Open table in a new tab IQR, interquartile range; NE, not estimable. *Kalinsky et al. ASCO 2023 abstr e18879. †Measured from index date. This RW analysis included patients with mTNBC treated with SG in 2L and later line settings since approval of SG in the US. SG showed survival benefit in this broad patient population. Follow-up duration was short for some pts in this analysis. As data will continue to mature over time, they will provide more insight into RW effectiveness of SG.