Correlation of molecular alterations with efficacy of everolimus in hormone-receptor–positive, HER2-negative advanced breast cancer: Results from BOLERO-2.

Abstract

142 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 univariate and multivariate Cox models. Results: NGS data (>250x coverage) were successfully generated from archival tumor specimens from 227 patients (NGS population, 157 in EVE + EXE arm and 70 in EXE arm) whose baseline characteristics and clinical outcome were comparable to the trial population (PFS HR = 0.40 and 0.45, respectively). The treatment benefit of EVE + EXE over EXE was maintained in the subgroups defined by each of the 9 genes with a mutation rate >10% (e.g., PIK3CA, FGFR1, CCND1) or when less frequently mutated genes (e.g., PTEN, AKT1) were included in their respective pathways. Patients with 0 or 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 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. The preliminary results 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. Clinical trial information: NCT00863655.