Comparison between alendronate and denosumab in preventing bone loss and lowering fracture risk related to adjuvant endocrine therapy (AET) for breast cancer: real-world data from a Third Level Centre experience.

Objectives: Adjuvant endocrine therapy (AET) for breast cancer treatment is associated with bone loss and increased fracture risk. This study evaluated variations in bone mineral density (BMD), trabecular bone score (TBS), biochemical parameters, and incidence of major fracture in a population of postmenopausal women on AET comparing denosumab 60 mg s.c/six months and alendronate 70 mg p.o/week.

Methods: After propensity-score matching, a population of postmenopausal women on AET was retrospectively evaluated comparing effects on BMD, TBS, bone turnover markers, and major fracture incidence (assessed by quantitative vertebral morphometry) after nearly 3-year follow up of denosumab 60 mg s.c. every 6 months and alendronate 70 mg p.o. every week (n=286, ratio 1:1) RESULTS: Denosumab group showed greater increase in total hip BMD (+0.034 g/cm2 vs +0.002 g/cm2; p<0.01), femoral neck BMD (+0.014 vs 0.000 g /cm2; p<0.01), lumbar spine BMD (+0.053 vs +0.005 g/cm²; p<0.01) and TBS (+0.017 vs -0.027; p<0.01) in comparison to alendronate. Treatment with denosumab was associated with 66% risk reduction of major fractures in comparison to alendronate (OR 0.34; p<0.01). There was no significant difference between groups in reducing fracture risk considering only patients with normal BMD at baseline.

Conclusions: Treatment with denosumab during AET improves BMD and TBS more than alendronate and is associated with greater reduction of major fractures in postmenopausal patients affected by osteopenia or osteoporosis.