SAT0361 Comparison of the efficacy of annual zoledronic acid or weekly alendronate. A 3-yr analysis of postmenopausal women with low bone mineral density

Background Osteoporosis remains as one of the leading cause of morbidity among postmenopausal women closely linked with higher risk of vertebral, hip and other fragility fractures. Treatment with bisphosphonates has been demonstrated to increase bone mineral density (BMD) and reduce the rate of abnormal fractures, but comparisons between them have not been assessed. Objectives Compare the change of BMD, in postmenopausal women with low BMD, between annual infusion of zoledronic acid and oral weekly alendronate. Methods Patients attending a postmenopausal Clinic in a third-referral Hospital in Mexico City was invited to participate, they must have low BMD diagnosed by densitometry and no other explanation for bone disease or previous fractures. They consented to be included and randomly receive 70 mg of alendronate (AL) weekly plus 1200 mg of calcium carbonate and 400 IU of vitamin D daily, or zoledronic acid (AZ) 5 mg I.V. annually, plus same dose of calcium and vitamin D. All women were seen every 3 months when compliance, side effects, and other relevant variables were recorded. They completed biochemical, spine radiography; comorbidities assessment and 2-region densitometry were on annual basis. All patients who completed a 3 year of follow-up were included for analysis. Due to the skewed distribution of BMD on hip and spine in both groups, non-parametric test were used for comparisons. Results Originally 59 patients were included in each group; at the third year, 43 remained in AL group and 58 in the AZ group. The main reason for drop-outs in the former group was low compliance, because they were excluded when 20% or more of the weekly AL doses were omitted. All were postmenopausal women with a mean age of 61±9.6 years. All patients basal BMD t-score in hip (median/interquartile range [IQR]) was -1.55/1.45, and in lumbar spine -1.9/1.0. The change BMD t-score in AL group went from -0.8/1.2 in baseline hip to -0.9/1.1 (p = NS), and -1.8/1.0 to -1.9/1.1 in lumbar spine (p=0.01); meanwhile, in the AZ group changes seen were as follows: in hip, from -1.2/1.3 to -1.1/1.1 (p=0.02), and in lumbar spine from -2.35/1.3 to -2.2/1.2 (p=0.001). Twenty percent of the AZ patients presented flu-like symptoms after the first infusion but did not occur after the subsequent infusions; 25 percent of AL group had gastrointestinal discomfort and required intermittent PPI drugs. Compliance in the AL group was declined over time, and at the end of the 3rd year, only 72% of the original patients remained in this group. Once out of protocol, patients required to be allocated in the AZ group. One hip fracture was recorded in the AL group, and two asymptomatic fractures among patients in the AZ group. Conclusions Annual zoledronic infusion seems to be superior to weekly oral alendronate in a group of Mexican postmenopausal women, for improving the BMD of hip and lumbar spine. Besides the individual drug efficacy, compliance with treatment (medical possession ratios) is an important variable to consider when deciding a treatment. References Chavez-Valencia V, Gallegos-Nava S, Arce-Salinas CA. Medical possession ratio and efficacy between zoledronic acid or weekly alendronate at one year, in post-menopausal women with low bone density. Ann Rheum Dis 2010;69(Suppl3):60 Disclosure of Interest None Declared