Correlation between PIK3CA mutations in cell-free DNA and everolimus efficacy in HR+, HER2- advanced breast cancer: results from BOLERO-2

Abstract

Background: The current analysis was performed to evaluate the impact of PIK3CA hotspot mutations on everolimus efficacy in BOLERO-2 participants, using cell-free DNA (cfDNA) from plasma samples collected at the time of patient randomisation.

Methods: PIK3CA H1047R, E545K, and E542K mutations in plasma-derived cfDNA were analysed by droplet digital PCR (ddPCR). Median PFS was estimated for patient subgroups defined by PIK3CA mutations in each treatment arm.

Results: Among 550 patients included in cfDNA analysis, median PFS in everolimus vs placebo arms was similar in patients with tumours that had wild-type or mutant PIK3CA (hazard ratio (HR), 0.43 and 0.37, respectively). Everolimus also prolonged median PFS in patients with PIK3CA H1047R (HR, 0.37) and E545K/E542K mutations (HR=0.30) with a similar magnitude.

Conclusions: Mutation analysis of plasma-derived cfDNA by ddPCR suggests that PFS benefit of everolimus was maintained irrespective of PIK3CA genotypes, consistent with the previous analysis of archival tumour DNA by next-generation sequencing.

Figure 1

Kaplan-Meier Plot of Progression-free Survival by PIK3CA mutation status. (A) PIK3CA wild-type vs hotspot mutations. (B) PIK3CA wild-type vs domain-specific hotspot mutations.