- A randomized controlled trial (RCT) finds that oral vs intravenous (IV) bisphosphonates have similar efficacy as adjuvant therapy for early breast cancer (eBCa).
Why this matters
- Their equivalence allows patient preferences to be satisfied.
- Treatment guidelines specify their use because when administered in a low estrogen environment, adjuvant bisphosphonates are associated with decreased BCa recurrence and death.
- This is the first RCT to perform a head-to-head comparison of oral vs IV bisphosphonates.
- RCT by SWOG S0307 comparing IV zoledronic acid (4 mg monthly for first 6 months; then every 3 months), oral clodronate (1600 mg daily), or oral ibandronate (50 mg daily).
- Primary outcome was 5-year disease-free survival (DFS).
- Funding: NIH; Berlex Pharmaceuticals; Roche/Genentech; Novartis Pharmaceuticals Inc; others.
- 73.3% of 6907 patients preferred oral bisphosphonates.
- No differences in DFS by log-rank test (P=.49).
- 5-year DFS:
- 88.3% (95% CI, 86.9%-89.6%) zoledronic acid.
- 87.6% (95% CI, 86.1%-88.9%) clodronate.
- 87.4% (95% CI, 85.6%-88.9%) ibandronate.
- 5-year OS: no differences.
- Bone as first site of recurrence did not differ between arms (P=.93).
- Grade 3/4 toxicity was similar: 8.8% (zoledronic acid), 8.3% (clodronate), and 10.5% (ibandronate) but osteonecrosis of the jaw was higher for zoledronic acid (1.26%) than clodronate (0.36%) and ibandronate (0.77%).
- None identified by authors.