A randomized, double-blind trial evaluating the palliative benefit of either continuing pamidronate or switching to zoledronate in patients with high-risk bone metastases from breast cancer (The Odyssey Study).

155 Background: Questions remain around the optimal use of bone-targeted agents (BTA) in patients with bone metastases (BM) from breast cancer (BC). In Canada pamidronate (PAM) is the most commonly used BTA in BC.We explored whether a switch to a more potent BTA, like zoledronic acid (ZA), in patients who remain at high risk of skeletal related events (SREs) despite PAM use is associated with significant palliative benefit. Methods: BC patients with high risk BM (prior SRE, bone progression, bone pain or levels of bone turnover marker serum C-telopeptide (sCTX) >400ng/L) despite >3 months of PAM use were eligible. Patients were randomized in a double–blind manner to either switch to ZA or continue on PAM every 4 weeks for 12 weeks. Primary outcome was the proportion of patients achieving a fall in sCTX at 12 weeks. Secondary outcomes were pain control (BPI and FACT-BP) and toxicity. Results 73 patients completed the study. Median age 61 years (range 37 – 87), prior duration of PAM use 10 months (range 3 –...