Abstract PS5-02-22: Impact of overall survival on the use of prophylactic granulocyte colony-stimulating factor with sacituzumab govitecan-hziy in the treatment of triple negative metastatic breast cancer patients

Abstract Background: Treatment options for metastatic triple-negative breast cancer (mTNBC) are limited, but antibody-drug conjugates (ADCs) such as sacituzumab govitecan (SG) have shown improved survival outcomes compared to single-agent chemotherapies. However, individuals undergoing this treatment are at an increased risk of neutropenia. Furthermore, updates to the package insert recommend primary prophylaxis with granulocyte-colony stimulating factor (G-CSF) for at-risk patients (pts). This study evaluated the impact of prophylactic G-CSF use on time to treatment discontinuation (TTD) and real-world overall survival (rwOS) among individuals with mTNBC who received SG. Methods: The IntegraConnect PrecisionQ de-identified electronic health record database, consisting of 3 million cancer pts across 500 care sites, was used to identify individuals with mTNBC that initiated SG between 4/22/2020 and 4/9/2025. Eligibility criteria included age ≥18 years at diagnosis and ≥2 documented visits. Prophylactic G-CSF was defined as any G-CSF use within 8 days following initiation of SG. Pts were excluded from the analysis if there was documentation of neutropenia (neutrophil count 1500/µL), discontinuation of SG, death, or censoring within 8 days of SG initiation. Demographic and clinical characteristics, including age at SG initiation, race, and Eastern Cooperative Oncology Group (ECOG) performance status, were assessed overall and stratified by prophylactic G-CSF use. Gray’s test was performed to assess cumulative incidence of neutropenia, adjusted for the competing risk of death, and 4-month estimates are reported. Kaplan-Meier survival curves were evaluated to assess TTD and rwOS by prophylactic G-CSF. To assess for the time-varying effect of prophylactic G-CSF use on TTD and rwOS, time-stratified multivariable Cox proportional hazards regression was performed with time-interval-specific effects (0-4 months, 4+ months) for prophylactic G-CSF use, and adjusted for additional demographic and clinical characteristics (age, race, ECOG status). Hazard ratios (HR) and 95% confidence intervals (CI) are reported. Results: Overall, 685 pts with mTNBC treated with SG were identified in the PrecisionQ database that met the study criteria. Most identified as White (67%), 41% had an ECOG status of 1, and 88% did not receive prophylactic G-CSF. Median age at SG initiation was 60 years (interquartile range IQR: 53, 69). Age, race, and ECOG status did not significantly differ by prophylactic G-CSF use. At 4 months, cumulative incidence of neutropenia was significantly higher among those who did not receive prophylactic G-CSF (42% vs. 30%, Gray’s test p=0.002). Median TTD and rwOS did not significantly differ by prophylactic G-CSF use. From 0-4 months, pts who did not receive prophylactic G-CSF were 2 times more likely to die compared to those who received prophylactic G-CSF within the first 8 days of SG initiation (HR: 2.37; 95% CI: 1.22-4.59 p=0.011). This impact was attenuated after 4 months (HR: 1.02, 0.79-1.50, p=0.4), indicating a time-varying effect of prophylactic G-CSF use on rwOS after SG initiation. There was no significant difference observed in TTD in either time-interval. Conclusions: Prophylactic use of G-CSF had a significant initial impact on rwOS among pts with mTNBC receiving SG. While prophylactic use of G-CSF did not confer a significant survival benefit after 4 months, the upfront effect warrants clinical consideration and integration into early treatment practices. These findings also indicate the need for further research assessing the impact of continued G-CSF use on overall survival. Citation Format: F. Kudrik, R. Choksi, V. Gorantla, S. Reddy, S. Reganti, S. Rosenfeld, G. Cioffi, E. Alwon, D. Parris, A. Rui, M. Gart, C. Wall, B. Wang, P. Varughese, J. Donegan, L. Morere, R. Geller, J. Scott, D. Patt. Impact of overall survival on the use of prophylactic granulocyte colony-stimulating factor with sacituzumab govitecan-hziy in the treatment of triple negative metastatic breast cancer patients 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 PS5-02-22.