Multicenter phase 2 trial of trifluridine-tipiracil for previously treated ER-postive HER2-negative metastatic breast cancer

Effective later-line chemotherapy options are scarce for patients with metastatic breast cancer (mBC). Trifluridine-tipiracil has show survival benefit in heavily pretreated patients with metastatic colorectal cancer and in gastric cancer refractory to a fluoropyrimidine. The multicenter phase 2 BOOG 2019-01 TIBET trial in The Netherlands evaluated trifluridine-tipiracil for patients with ER-positive HER2-negative mBC, who had previously been treated with capecitabine and up tot two other lines of chemotherapy, including a taxane. The primary endpoint was met, with a disease control rate at 8 weeks of 64% (95% CI 50.1-75.9). The median progression-free survival and overall survival were 5.4 months (95% CI 2.0-7.2) and 14.0 months (8.8-17.8), respectively. There were no unexpected toxicities and no grade 5 treatment-related adverse events. Quality of life scores remained stable throughout treatment. The authors conclude that trifluridine-tipiracil demonstrated promising efficacy in pretreated patients with ER-positive, HER2-negative mBC.