Abstract P2-14-01: Fulvestrant vs exemestane for treatment of metastatic breast cancer in patients with acquired resistance to non-steroidal aromatase inhibitors – a meta-analysis of EFECT and SoFEA (CRUKE/03/021 & CRUK/09/007)
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AbstractBackground: Optimal endocrine treatment (trt) for post-menopausal women with ER+ advanced breast cancer (ABC) progressing on or following a non-steroidal (NS) aromatase inhibitor (AI) is unclear. The EFECT study showed no difference in efficacy between the steroidal antiestrogen fulvestrant (F) & steroidal AI exemestane (E) in this setting (HR = 0.96, 95%CI: 0.82, 1.13; p = 0.65). Pre-clinical data suggest F may be more effective in a low estrogen environment. SoFEA investigated F combined with anastrozole (F+A) in patients (pts) with acquired resistance to previous AI compared with F alone & F alone vs. E. The combination of F+A was no better than F (HR = 1.00, 95%CI: 0.83, 1.21; p = 0.98) nor F alone better than E (HR = 0.95, 95%CI: 0.79, 1.14; p = 0.56); the lack of added benefit for F+A is consistent with previous 1st-line studies that have assessed this combination versus A alone (FACT & SWOG-S0226).Methods: SoFEA is a multi-center partially blinded randomized phase III study postmenopausal women were allocated to F plus A (F+A n=243), F plus placebo (n = 231) or E (n = 249). Similarly, EFECT is a randomized, double-blind, placebo controlled, multi-center phase III trial of F (n = 351) versus E (n = 342) in postmenopausal women (see table). However, given the differences in prior endocrine therapy/responsiveness within SoFEA & EFECT populations, an individual pt meta-analysis combining data from SoFEA & EFECT will be conducted enabling exploration of putative effects within specific pt subgroups to establish evidence in support, or not, of a pt subgroup sensitive to F at the dose used in these trials. Subgroups to be analysed include receptor status, visceral involvement, AI sensitivity, age, NSAI setting & time on NSAI.Results: 723 pts (480 in F & E) were enrolled from 82 UK & 4 South Korean centers (03/2004-04/2010) in SoFEA. 693 pts were enrolled from 138 centers worldwide (08/2003-11/2005) in EFECT. Trt was well tolerated in both trials; serious adverse events were rare. The meta-analysis will be conducted in July 2012 & results presented.Conclusion: Combining individual pt data from SoFEA & EFECT via meta-analysis will provide definitive clinical information on pt's response to F at the dose used in these studies, in particular whether certain pts with acquired resistance to NSAI do experience benefit of use of this antiestrogen as opposed to E.Citation Information: Cancer Res 2012;72(24 Suppl):Abstract nr P2-14-01.
