Statistical analysis
REGRESSION
Trastuzumab plus vinorelbine was the backbone treatment for trastuzumab-pretreated patients in 2019 in China; thus, the median PFS (5.78 months) of the control group in BOLERO-3 was considered as the historical control in our study [Efficacy and safety were analyzed in all patients with at least one dose of study drug. Continuous variables were expressed as median (range), and categorical variables were expressed as frequency (percentage). The 95% confidence intervals (CIs) of ORR and DCR were calculated using the Clopper-Pearson method. Comparison of ORR was performed between subgroups using the chi-square test. Median PFS and OS were estimated using the Kaplan–Meier method, and their 95% CIs were calculated using the Brookmeyer-Crowley method. Comparison of PFS was performed between subgroups using the Cox proportional hazard regression model. All statistical analyses were performed using SAS version 9.4 (SAS Institute, Cary, NC, USA). Two-sided 