Efficacy and safety of trilaciclib plus chemotherapy in metastatic triple-negative breast cancer: A systematic review and meta-analysis.

439 Background: Chemotherapy-induced myelosuppression remains a major dose-limiting toxicity in cancer treatment, resulting in neutropenia, anemia, and thrombocytopenia that adversely affect patient outcomes. Trilaciclib, an intravenous CDK4/6 inhibitor administered prior to chemotherapy, has emerged as a myeloprotective agent. While its efficacy has been demonstrated in small-cell lung cancer, its role in metastatic triple-negative breast cancer (mTNBC) requires further evaluation. This systematic review aims to assess the efficacy and safety of trilaciclib in patients with mTNBC. Methods: A comprehensive literature search was conducted across PubMed, Embase, ClinicalTrials.gov, the EU Clinical Trials Register, and Cochrane Library from inception to April 2025. Outcomes assessed included overall survival (OS), objective response rate (ORR), incidence of severe neutropenia (SN), red blood cell (RBC) transfusions after week 5, and treatment-emergent adverse events (TEAEs). Meta-analyses were performed using R version 4.5.0. Results: Eleven studies were included in the final quantitative synthesis. Trilaciclib was associated with a significant reduction in the incidence of SN (OR=0.18; 95% CI 0.12–0.27), anemia (OR=0.45; 95% CI 0.32–0.64), and RBC transfusions (OR=0.52; 95% CI 0.33–0.82). Reductions were also observed in rates of grade ≥3 adverse events (OR=0.49; 95% CI 0.25–0.95), grade 4 adverse events (OR=0.23; 95% CI 0.14–0.37), and hospitalization (OR=0.56; 95% CI 0.37–0.85). No significant differences were observed in rate of treatment discontinuation (OR=1.03; 95% CI 0.72–1.48), thrombocytopenia (OR=0.81; 95% CI 0.62–1.07), or ORR (OR=0.89; 95% CI 0.56–1.41). However, trilaciclib was associated with an increased risk of infusion-related adverse events (OR=2.81; 95% CI 1.09–7.21). Conclusions: Trilaciclib significantly reduces chemotherapy-induced hematologic toxicities in mTNBC without negatively impacting antitumor efficacy. However, its effects on survival outcomes remain uncertain and warrant further investigation.