In the entire trial population, median progression-free survival was 6.9 months with buparlisib and 5.0 months with placebo (hazard ratio, 0.78; P less than .001), meeting the trial’s primary endpoint.
In the subset of 372 patients with PI3K activation that was defined by presence of a PIK3CA mutation of any type (activating or not) and/or PTEN loss in archival tumor tissue, median progression-free survival was 6.8 months with buparlisib and 4.0 months with placebo (HR, 0.76), but the P value missed the threshold for significance in this analysis.
In a preplanned exploratory analysis, the investigators analyzed circulating tumor DNA in 587 patients for two PIK3CA mutations known to be activating mutations. Results here suggested that the progression-free survival benefit was limited to those who had a mutation – 7.0 months with buparlisib vs. 3.2 months with placebo (HR, 0.56; P less than .001) – with no significant benefit in patients having the wild-type (nonmutated) gene.