Background: Everolimus(EVE)plus exemestane(EXE)more than doubled progression-free survival(PFS)while maintaining quality of life vs EXE alone in postmenopausal women with hormone-receptor positive(HR+),HER2-negative(HER2-)advanced breast cancer(BOLERO-2 phase Ⅲ; NCT00863655).PFS benefit was seen in all clinically defined subgroups.We evaluated genetic variations of a broad panel of cancer-related genes and explored their correlations with EVE benefit.Methods: Exon sequence and gene copy number variations were analyzed in 182 cancer-related genes by next-generation sequencing(NGS).Correlations with PFS were evaluated using both univariate and multivariate Cox models.Results: NGS data(>250x coverage)were successfully generated from archival tumor specimens from 227 patients(NGS population,157 and 70 in EVE+EXE and EXE arms,respectively)whose baseline characteristics and clinical outcome were comparable with the trial population(PFS HR = 0.40 and 0.45,respectively).The treatment benefit of EVE+EXE over EXE is maintained in the subgroups defined by each of the nine genes with a mutation rate >10%(eg,PIK3CA,FGFR1,and CCND1),or when less frequently mutated genes(eg,PTEN,AKT1)were included in their respective pathways.Patients with no or only 1 genetic alteration in PI3K or FGFR pathways,or CCND1,had a greater treatment effect from EVE(HR = 0.27,95%CI 0.18-0.41,adjusted by covariates,in 76%of the NGS population),indicating the value of these pathways for predicting sensitivity/resistance to EVE in this setting.Conclusions: This is the first global registration trial in which efficacy-predictive biomarkers were explored by correlating broad genetic variations with clinical efficacy.It demonstrated the feasibility of applying large-scale NGS and subsequent correlative analysis to such trials.The observations suggest that a large subgroup of patients(76%),defined by minimal genetic variations in the PI3K or FGFR pathways,or CCND1,derives the most benefit from EVE therapy(HR = 0.27 vs 0.40 for the full NGS population).These exploratory results and their implication in understanding the interplay of multiple pathways in tumor cells and testing new hypotheses for targeted combination therapies in HR+/HER2-BC will be further investigated.