Abstract P2-09-12: A single-blind, randomized, placebo-controlled phase II study to evaluate the impact of oral ibandronate on bone mineral density in osteopenic breast cancer patients receiving adjuvant aromatase inhibitors: Final results of the single-center BONADIUV trial

Abstract

Abstract Background. Several randomized trials demonstrated aromatase inhibitors (AI) superiority in terms of disease-free survival compared to tamoxifen treatment for postmenopausal hormone receptor-positive breast cancer (BC) patients. Anyway AI toxicity profile due to estrogen suppression is a concern. Pivotal trials demonstrated a significant bone mineral density (BMD) loss due to AI, with a consistent risk of fractures, thus impacting on patients' quality of life. Bisphosphonates represent an effective treatment in postmenopausal osteoporosis fractures prevention. Several studies demonstrated that upfront bisphosphonates therapy prevents bone loss in postmenopausal women receiving adjuvant AI for early-stage BC. However an adequate patients selection for adjuvant bisphosphonates treatment during AI endocrine therapy is still a challenge. We present the final results of the BONADIUV trial, a single-blind, randomized, placebo-controlled phase 2 study designed to evaluate the impact of ibandronate treatment on BMD in osteopenic women taking AI. Methods. Between January 2011 and May 2014, 561 patients underwent a baseline BMD assessment before starting AI as planned adjuvant treatment. Overall 171 osteopenic patients (lumbar spine [LS] and/or trochanter -1< T-score <-2.5), were randomized in a 1:1 ratio to receive either placebo or oral monthly ibandronate (150 mg). All patients receive oral supplementation of calcium and vitamin D3. Study duration was 2 years. Exclusion criteria were: premenopausal status at time of randomization; comorbidities with increased risk of osteoporosis; body mass index <18; chronic use of steroids; previous use of bisphosphonates; psychiatric disorders. Primary endpoint was the mean BMD difference between the two arms at a 2-year follow up. ClinicalTrials.gov identifier: NCT02616744. A total of 72 patients per arm of treatment were needed to obtain an 85% statistical power in order to detect a 2% BMD mean difference between the two arms. Considering a 10% dropout, at least 158 patients were required. Results. A total of 171 patients were randomized in the study. Overall 27 patients (15.8%) withdrew the protocol (17 ibandronate vs 10 placebo arm): the final analysis was performed on 144 patients (72 patients per arm). P-value from Wilcoxon test showed no significant difference between arms at baseline both for LS (p=0.94) and trochanter (p=0.83). At 2-year, osteopenic patients treated with ibandronate gained +18.7% and +15.5% at the LS and trochanter BMD, respectively. Patients treated with placebo lost -13.3% at the LS, and gained +2.9% at the trochanter. Trochanter p-value from covariance analysis showed a mean BMD change significantly in favor of ibandronate arm at 1-year (p=0.012), and borderline at 2-year (p=0.087). Concerning LS, the mean BMD change was significantly in favor of ibandronate arm both at 1-year (p=0.002) and 2-year (p<0.0001). Conclusions. Final results of our study showed that treatment with ibandronate, as compared to placebo, improved BMD change in osteopenic women treated with adjuvant AI, and consistently protected patients' bone loss. Citation Format: Livi L, Saieva C, Desideri I, Scotti V, De Luca Cardillo C, Carta G, Cecchini S, Orzalesi L, Sanchez LJ, Casella D, Bernini M, Nori J, Bianchi S, De Feo ML, Meattini I. A single-blind, randomized, placebo-controlled phase II study to evaluate the impact of oral ibandronate on bone mineral density in osteopenic breast cancer patients receiving adjuvant aromatase inhibitors: Final results of the single-center BONADIUV trial [abstract]. In: Proceedings of the 2016 San Antonio Breast Cancer Symposium; 2016 Dec 6-10; San Antonio, TX. Philadelphia (PA): AACR; Cancer Res 2017;77(4 Suppl):Abstract nr P2-09-12.