SWOG S0307 phase III trial of bisphosphonates as adjuvant therapy in primary breast cancer: Comparison of toxicities and patient-stated preference for oral versus intravenous delivery.

558 Background: Bone metastases are a common site of distant recurrence in breast cancer. Evidence from randomized trials, including a recent meta-analysis, suggests that adjuvant bisphosphonates can decrease recurrence and death. SWOG S0307 compares efficacy of 3 bisphosphonates in early stage breast cancer. Methods: Patients with stage I-III breast cancer receiving adjuvant systemic therapy were randomized to receive 3 years of clodronate (CLOD) (1600 mg po qd), ibandronate (IBAN) (50 mg po qd) or zoledronic acid (ZA) (4 mg IV q month x 6, then q3 months x 2.5 years). The primary endpoint is disease-free survival. Overall survival, sites of first recurrence, and adverse events are secondary endpoints. Results: Between Nov 2005 and Feb 2010 6,097 patients were enrolled. Survival data are maturing with 50% of the expected events occurring to date. Annual interim analyses are being conducted. 5,752 patients are assessable for toxicity. Median age was 53. 78% of tumors were ER positive, 16% HER2 positive, 1...