Background
Phase III, open-label RCT. N=543 HR+ HER2- metastatic breast cancer with 2–5 prior systemic lines including prior taxane, CDK4/6 inhibitor, and endocrine therapy. Sacituzumab govitecan (SG) is an anti-Trop-2 ADC delivering SN-38 (active irinotecan metabolite) via a labile linker enabling bystander effect.
Interventions and follow up
Arm A: Sacituzumab govitecan 10mg/kg IV days 1 and 8 of 21-day cycle
Arm B: Physician's choice chemotherapy (eribulin, vinorelbine, capecitabine, or gemcitabine)
Primary endpoint: Progression-free survival (PFS)
mFollow up: 10.2 months
Arm B: Physician's choice chemotherapy (eribulin, vinorelbine, capecitabine, or gemcitabine)
Primary endpoint: Progression-free survival (PFS)
mFollow up: 10.2 months
Results
PFS: 5.5 vs 4.0mo, HR 0.66, 95% CI 0.53–0.83, P<.001
OS: 14.4 vs 11.2mo, HR 0.79, 95% CI 0.65–0.96, P=.020
ORR: 21.0% vs 14.0%
OS: 14.4 vs 11.2mo, HR 0.79, 95% CI 0.65–0.96, P=.020
ORR: 21.0% vs 14.0%
Adverse events
Hematologic: Grade ≥3 neutropenia 51.4% vs 38.4%; grade ≥3 anemia 10.3% vs 8.3%; febrile neutropenia 5.9% vs 3.4%
GI: Grade ≥3 diarrhea 10.3% vs 1.5%
Dermatologic: Alopecia 38.3%
Tolerability: Discontinuation 5.5% vs 3.9%
GI: Grade ≥3 diarrhea 10.3% vs 1.5%
Dermatologic: Alopecia 38.3%
Tolerability: Discontinuation 5.5% vs 3.9%
Conclusions
Sacituzumab govitecan significantly improved PFS and OS vs chemotherapy in heavily pretreated HR+ HER2- mBC, becoming the first ADC to demonstrate an OS benefit in this subtype. Supports its use as a later-line option after CDK4/6i and endocrine therapy exhaustion.
Key Limitations
Modest absolute benefit (1.5mo PFS, 3.2mo OS) in heavily pretreated patients. High grade ≥3 neutropenia (51%) requires G-CSF support; UGT1A1*28 homozygotes have higher SN-38 toxicity and may need dose reductions. Trop-2 expression not used for selection — optimal biomarker threshold unclear. T-DXd has moved into earlier lines for HER2-low, altering SG positioning.
Clinical Context
Sacituzumab govitecan (Trodelvy): FDA regular approval 2023 for HR+ HER2- mBC after ≥2 prior lines including endocrine therapy and CDK4/6i. ESMO-MCBS 3. With T-DXd approved for HER2-low in earlier lines, SG is increasingly used in HER2-zero or HER2-low post-T-DXd patients. UGT1A1 genotyping should be considered before initiation.
References