Statistical analysis
visceral disease
EVENTS, METASTASES
Assuming a median PFS of 9.9 months in the placebo group based on the subgroup analysis of the BOLERO-2 study for those without visceral disease [The primary analysis of PFS was planned to be conducted after 40 PFS events had occurred per independent review. Subgroup analyses of PFS were undertaken by independent review and supportive investigator assessment. Key prespecified subgroups were: presence of baseline bone-only metastases (yes vs no), prior CDK4/6 inhibitor treatment (yes vs no) and menopause status (pre vs post). A stratified Cox proportional hazards model was used to estimate the hazard ratio and its asymptotic two-sided 95% Wald CI between the two treatment groups (with a hazard ratio less than one favouring xentuzumab in combination with everolimus and exemestane). The primary efficacy analyses were performed on the randomised set (all randomised patients) and safety analyses were based on the treated set (all patients treated with at least one dose of any study treatment). As the trial was stopped early, no confirmatory statistical testing was possible, so the p-values are exploratory.