Ibandronate reduces skeletal morbidity in patients with breast cancer

Three phase III studies have assessed the efficacy of intravenous (IV) and oral ibandronate over 96 weeks for metastatic bone disease in patients with breast cancer. The primary endpoint for each trial was the skeletal morbidity period rate, defined as the number of 12-week periods with new bone complications, adjusted for the time spent on study. Both IV ibandronate 6 mg every 3 to 4 weeks and oral ibandronate 50 mg once daily significantly reduced the skeletal morbidity period rate compared with placebo ( P = .004 in each case). The studies were not powered to detect statistical significance on individual components of the skeletal morbidity period rate. Nevertheless, IV ibandronate significantly reduced vertebral fractures and the need for radiotherapy, while oral ibandronate led to significantly fewer bone events needing radiotherapy or surgery than placebo. Using a multivariate Poisson regression model, the mean reduction in the relative risk of new bone events compared with placebo was 40% with IV ibandronate 6 mg ( P = .0033), and 38% with oral ibandronate 50 mg ( P <.001). The clinical equivalence of IV and oral ibandronate was confirmed by a post-hoc Anderson-Gill analysis of time to multiple skeletal events. These results show that IV and oral ibandronate effectively reduce skeletal morbidity in breast cancer patients with bone metastases.