Effectiveness and Safety of Sacituzumab Govitecan in Real-World Clinical Practice in Patients with Metastatic Triple-Negative and HR+/HER2-Negative Breast Cancer

Background/Objectives: Sacituzumab govitecan (SG) is an antibody–drug conjugate targeting Trop-2 that has demonstrated clinical benefits in randomised trials for patients with metastatic triple-negative breast cancer (mTNBC) and metastatic hormone receptor-positive/HER2-negative (HR+/HER2− mBC) disease. However, real-world data on its effectiveness and safety are limited, especially in patients with poor performance status or central nervous system (CNS) involvement. This study aimed to evaluate the real-world outcomes of SG in these two subtypes. Methods: We conducted a retrospective, multicentre, observational study across three tertiary hospitals in Spain. Patients with mTNBC or HR+/HER2− mBC treated with SG between June 2022 and March 2025 were included. Clinical data, treatment history, adverse events (AEs), and survival outcomes were also recorded. The median progression-free survival (mPFS) and median overall survival (mOS) were estimated using Kaplan–Meier analysis. Univariate and multivariate analyses were performed to identify the factors influencing outcomes. The association between granulocyte colony-stimulating factor (G-CSF) prophylaxis and neutropenia was assessed using Fisher’s exact test. Results: A total of 56 patients were included in this study (33 with mTNBC and 23 with HR+/HER2− mBC). In the mTNBC group, mPFS was 4.0 months (95% CI: 1.94–5.98) and mOS was 11.0 months (95% CI: 4.80–17.12). In the HR+/HER2− mBC group, mPFS was 3.7 months (95% CI: 2.02–5.44) and mOS was 20.2 months (95% CI: 3.9–36.5). Fatigue, neutropenia, and gastrointestinal toxicity were the most common AEs. Primary G-CSF prophylaxis was not associated with a reduced incidence of neutropenia (p = 0.434). Conclusions: In routine practice, SG shows effectiveness comparable to that of randomised trials across both subtypes, with a safety profile consistent with pivotal studies. The observed toxicity profile was consistent with that described in pivotal clinical trials and other studies. The prophylactic use of G-CSF was not associated with an impact on the occurrence of neutropenia, but the incidence of neutropenia was lower than that in clinical trials and other studies that did not administer G-CSF prophylactically.