Effect of risedronate on hip structural geometry: a 1-year, double-blind trial in chemotherapy-induced postmenopausal women.
INTRODUCTION
Chemotherapy-induced menopause is associated with bone loss. The effect on structural geometry is unknown. Our objective was to determine if oral bisphosphonate therapy could maintain or improve femoral geometry in breast cancer patients with chemotherapy-induced menopause.


METHODS
This preplanned 1 year interim, secondary analysis of the Risedronate's Effect on Bone loss in Breast CAncer Study (REBBeCA Study) examined hip structure analysis (HSA), i.e. changes in the bone cross-sectional area (bone CSA), section modulus (SM: measure of bending strength), cortical thickness (CT) and buckling ratio (BR: index of cortical bone stability), in a double-blind trial of 87 newly postmenopausal, nonmetastatic breast cancer patients, randomized to risedronate, 35 mg once weekly (RIS) versus placebo (PBO).


RESULTS
After 12 months, intertrochanteric parameters demonstrated percentage improvement (RIS vs. PBO) from baseline in bone CSA (mean+/-SD: 4.25+/-6.29 vs. 0.60+/-5.99%), SM (3.97+/-6.40 vs. 0.80+/-7.08%), and CT [5.20+/-6.98 vs. 1.13+/-6.87% (all p-values <0.05 except SM p=0,0643)]. Similar improvements were observed at the femoral shaft [bone CSA: 2.24+/-5.74 vs. -0.78+/-5.73%; SM: 1.62+/-6.23 vs. -1.39+/-7.06%; CT: 3.79+/-7.84 vs. -0.17+/-7.90% (all p-values <0.05, RIS vs. PBO, except SM p= p =0.0568)]. At both sites, the BR had significant decreases consistent with improved strength.


CONCLUSION
We conclude that RIS improves measures of hip structural geometry in women with breast cancer following chemotherapy.