Abstract PS5-03-29: A retrospectIve observatioNal multicenter study on SacItuzumab Govitecan in mTNBC post NHIA reimbursement in Taiwan (inSiGht)- An interim analysis

Abstract Background Sacituzumab govitecan (SG), a Trop-2-directed antibody-drug conjugate, is approved globally for second-line (2L) or later treatment of unresectable locally advanced or metastatic triple-negative breast cancer (mTNBC) and HR+/HER2- mBC. However, pivotal trials largely included Western populations. Given known ethnic differences in mTNBC biology and treatment responses, evaluating SG’s real world effectiveness and safety in Asians is crucial. SG was approved in Taiwan in Nov 2022 and reimbursed by the National Health Insurance in Feb 2024. This interim analysis from the inSiGht study provides early real-world data in Taiwanese mTNBC patients post-reimbursement. Methods This retrospective analysis included mTNBC patients treated with SG in the ≥2L setting in Chang Gung Memorial Hospital Breast Cancer Registry (Taipei, Linkou and Tucheng) from Feb 2024 to Apr 2025. Clinical characteristics, treatment outcomes, and adverse events were assessed. Kaplan-Meier estimates on treatment outcomes and subgroup analyses by treatment line were performed. Results Among 42 patients (median age: 56 years); 15 received SG as 2L and 27 as third-line or later (3L+). ECOG 0-1 was reported in 90.5% (2L: 86.7%; 3L+: 92.6%). Visceral metastases were present in 90.5% (2L: 86.7%; 3L+: 92.6%) and brain metastases in 21.4% (2L: 26.7%; 3L+: 18.5%). HER2-low expression was seen in 47.6% (2L: 53.3%; 3L+: 44.4%), and 52.4% were HER2 IHC 0. Prior PD-L1 inhibitor use was reported in 28.6% (2L: 46.7%; 3L+: 18.5%). Median time from mTNBC diagnosis to SG initiation was 11 months (2L: 6.2 months; 3L+: 15 months). Median rwPFS was 5 (95%CI: 2.6, 8.8) months overall. By line of treatment, median rwPFS was 9.0 (95%CI: 2.6, NR) months in 2L and 3.8 (95%CI: 2.3, NR) months in 3L+. Median follow up was 9 months (IQR 6.4, 13.8). The 9-month OS rate (95% CI) was 73% (59- 89%) overall, with higher OS in 2L (92% [79-100%]) vs. 3L+(61% [43-85%]). Among 33 patients with response data, 36.4% achieved partial response (PR), 27.3% had stable disease (SD) and 36.4% showed progression. PR rate was higher in 2L (53.8%) vs. 3L+ (25.0%). Progression occurred more in 3L+ (45.0%) vs. 2L (23.1%). Among patients who discontinued SG, the primary reason was disease progression (79.3%), followed by death (13.8%) and adverse events (6.9%). Notably, none of the 2L patients discontinued due to adverse events. Grade 2 diarrhea occurred in 7.1%, grade 1 in 16.7%. Grade 3 and 4 neutropenia were observed in 4.8% each. Granulocyte colony-stimulating factors use was reported in 23.8% of patients. Conclusion This interim analysis demonstrates the real-world effectiveness and tolerability of SG in Asian patients with mTNBC. Effectiveness outcomes are particularly encouraging when SG is used earlier in the treatment course and are comparable to those observed in the ASCENT trial. These findings support SG’s clinical value in Asian populations, including those with aggressive disease features such as brain and visceral metastases. Further follow up will help confirm these observations as additional data mature. Citation Format: H. Chou, M. Peng, W. Kuo, S. Shen, C. Yu, W. Shen, C. Yang, H. Kuo, H. Lin, D. F. Lin, M. Wang, N. Sadetsky, Y. Lin, S. Chen. A retrospectIve observatioNal multicenter study on SacItuzumab Govitecan in mTNBC post NHIA reimbursement in Taiwan (inSiGht)- An interim analysis [abstract]. In: Proceedings of the San Antonio Breast Cancer Symposium 2025; 2025 Dec 9-12; San Antonio, TX. Philadelphia (PA): AACR; Clin Cancer Res 2026;32(4 Suppl):Abstract nr PS5-03-29.