Sacituzumab Govitecan initial dose reduction in polish patients with metastatic triple-negative breast cancer: impact on efficacy and safety.

BACKGROUND: Sacituzumab govitecan (SG) is approved for metastatic triple-negative breast cancer in ≥ 2 line setting at 10 mg/kg IV on Days 1 and 8 (21-day cycle). Trials confirmed its superiority over 8 mg/kg with manageable safety. In practice, precautionary dose reductions are used despite no formal guidance. In Poland, fixed 200 mg vials and unreimbursed drug waste lead to early dose adjustments. METHODS: This retrospective study evaluated the impact of initial SG dose reduction on treatment outcomes and tolerability in Polish patients. Medical records provided data on baseline features, treatment, survival, and safety. Kaplan-Meier and chi-square tests were used for survival and group comparisons. A multivariate Cox model assessed the independent effect of dose reduction on overall survival (OS) and progression-free survival (PFS). Significance was set at p < 0.05. RESULTS: Among 83 patients (median age 55, range 30-86), initial dose reductions ≥ 10% were observed in 16 patients (19.3%), including 9 (10.8%) with dose reduced ≥ 20%. Administrative adjustments (reductions > 10% to flat doses of 200 mg multiplications) accounted for 18.1% of the entire cohort. Grade ≥ 2 and ≥ 3 adverse events occurred in 83.1% and 56.6%, respectively. In a multivariate analysis, a ≥ 20% initial dose reduction remained an independent predictor of shorter PFS (HR: 2.6; 95% CI: 1.1-6.6; p = 0.04) and OS (HR: 6; 95% CI: 2-17.5; p = 0.001). Initial dose reduction did not affect toxicity. CONCLUSIONS: In this preliminary report initial dose reduction of SG negatively impacted PFS and OS without reducing toxicity, highlighting the need for further studies and dosing policy adjustments.