Bone Abstracts

Objectives: From late 2015 a new protocol for zoledronic acid was adopted in our centre. This led to many children changing from pamidronate (PAM) to zoledronic acid (ZA) treatment. In a minority of cases the children and/or their families felt strongly that they wanted to change back to PAM. We present the characteristics of that minority and how bone turnover markers (BTMs) and bone mineral densities (BMD) changed whilst on ZA.

Method: From Nov 2016 to Oct 2018, 9/29 children changed back to PAM from ZA. We retrospectively reviewed their clinical records.

Results: Diagnoses were: osteogenesis imperfecta x4; other osteoporosis x2; Ehlers Danlos x1; fibrous dyplasia x1; Duchenne muscular dystrophy x1. Median duration on PAM pre-ZA was 2.3 yrs (1.1–7.7 yrs). Median period of time on ZA was 0.8 yrs (0.5–2.0 yrs). Median number of doses before reversion to PAM was 2 (1–4); 8/9 were on 6 monthly ZA. Median age at time changed back to PAM 13.7 yrs (3.6–17.9 yrs). Reason for reversion in vast majority (7/9) was less effective pain relief ± more fatigue. Others reported deterioration in sleep and mobility or increased appetite. Whilst on ZA: median annualised % change in serum ALP (n=8) −1.5% (−120% to +61%); median annualised % change in urine NTx (n=8) −14% (−82% to +243%); and median annualised % change in L2-4 BMD (n=8) 7% (+1% to +37%). Unsurprisingly, the longer an individual had been on PAM the smaller the % change in BMD on ZA and, correspondingly, the younger the individual the greater the reduction in NTx.

Conclusion: Whilst there was a broadly consistent view expressed by the respective children and parents that ZA was less effective at managing symptoms, there was no corresponding consistency of change in BTMs or BMD. Our clear impression is that there are some children who appear to obtain greater symptomatic benefit from PAM compared to ZA and vice versa. The biological basis for this is unclear. Over time, our practice has evolved and we are now more likely to offer 3 monthly ZA even to older children in whom 6 monthly ZA fails to control symptoms.

Disclosure: Nick Bishop: Consults for Alexion, Mereo, UCB and Amgen, and receives grant support for clinical studies from Alexion and Amgen. Paul Arundel: Research grant/honoraria/ expenses – Alexion and Kyowa Kirin. Expenses – BioMarin.