Fulvestrant plus vandetanib versus placebo for the treatment of patients with metastatic breast cancer resistant to aromatase inhibitor therapy (FURVA): a multicentre, Phase 2, randomised controlled trial

Background FURVA, a randomised, double-blind Phase II trial, investigated whether the addition of vandetanib to fulvestrant improved progression-free survival (PFS) in patients with an aromatase inhibitor(AI)-resistant advanced breast cancer. Methods Postmenopausal women with oestrogen receptor-positive (ER+ve)/HER2-negative advanced breast cancer, who experienced disease progression on an AI, were randomised (1:1) to fulvestrant 500 mg (Q28) with vandetanib 300 mg od (f + v) or placebo (f + p) until disease progression or discontinuation. The primary endpoint was PFS; secondary endpoints included overall survival (OS) and the influence of REarranged during Transfection (RET) signalling on outcomes. Results In total, 165 participants were randomised to f + v ( n = 80) or f + p ( n = 85). Median PFS was 5.5 months (m) for f + v compared to 5.5 m for f + p (hazard ratio (HR) 0.88; 95% CI: 0.62–1.23; P = 0.22). Unexpectedly, high total RET expression was associated with a PFS advantage of 8.87 m vs 3.94 with low RET (HR 0.493: 95% CI 0.32–0.77; P = 0.002) independent of the treatment arm, supported by an OS advantage 21.95 m vs 18.04 (HR 0.584; 95% CI 0.34–1.00; P = 0.051) in the high-RET group. Conclusion The addition of vandetanib to fulvestrant does not improve PFS. However, high total RET expression was associated with improved PFS, suggesting RET may have a prognostic role in patients treated with fulvestrant. Clinical trial registration ClinicalTrials.gov, NCT02530411.