Bone Abstracts

Introduction: Reduced bone mineral density [BMD] and increased fracture risk are common complications in all conditions characterized by severely reduced physical activity and/or requiring long-term glucocorticoid [GC] treatment, including Duchenne Muscular Dystrophy [DMD].

Objectives: The RisBo-DMD study (EudraCT 2011-005745-12) is a 24-month prospective multicenter study, aimed at identifying DMD patients at higher risk of fractures and improving the bone treatment strategy.

Methods: At baseline, 12 and 24 months: DXA spine (LS) and total-body-less-head (TBLH) bone mineral density [BMD] measurement; spine X-rays for vertebral fractures; biochemical tests for bone metabolism, including bone turnover markers (CTx, NTx, OC, BAP) and bone-related cytokines (RANKL, OPG, DKK1, IL6). Months 1-12-24: all patients treated with calcifediol (0.8 μg/kg/die) and instructed to adequate dietary calcium intake to the RDA. 12-month assessment: Patients at ‘high risk’ of fractures identified based on: baseline BMD Z-score ≤–1.5; history of previous fractures; incident fractures; increased bone resorption markers for age; BMD yearly increase ≤5%. Months 12–24: patients at high risk of fractures treated with i.v. zoledronate infusion every 3 months (first dose 0.0125 mg/kg; subsequent doses 0.025 mg/kg).

Results: 54 patients were enrolled. At baseline evaluation, we observed low spine BMD (Z-score −2.19±1.10); intermediate levels of serum 25-OH D (39.5±27.9 ng/ml); high levels of bone resorption markers (serum CTx 721.7±323.9 pg/ml; urinary NTx 498.7±439.1 nMBCE/mMCrea). After 24 months, there were 3 appendicular and 2 vertebral fractures in patients not treated with bisphosphonate, while no incident fractures in patients treated with zoledronate. We observed a general improvement in both LS and TBLH BMD and in LS BMC (P<0.001 for all), while the LS Z-score increased (−0.85±2.76; NS) only under zoledronate. General increase in 25-OH D levels (57.36±34.21 ng/mL; P=0.0025) and reduction of NTx (352.24±386.5 nMBCE/mMCrea; P<0.001) were found, while only in the zoledronate-treated group CTx and OC decreased (233.1±195.7 pg/mL, P=0.02; 18.1±13.5 ng/ml, P=0.0099).

Conclusions: These results indicate that adequate dietary calcium intake plus calcifediol is a valuable first-line treatment to improve bone metabolism in GC-treated DMD patients. The addition of zoledronate in patients with more severe bone alterations and a higher risk of fractures is a further improvement.

Disclosure: The authors declared no competing interests.