Aneurysmal bone cyst (ABC) is a benign tumour whose progression involves the RANK/RANKL signalling pathway. Surgery is the reference standard treatment but carries risks that vary with the site of the tumour. Denosumab is a human monoclonal IgG2 antibody that targets the RANK/RANKL pathway and may therefore hold promise for inhibiting ABC progression. The objective of this study was to evaluate denosumab use in paediatric patients (younger than 18 years) with ABC and to describe the clinical and radiological outcomes, as well as the side effect profile.

Denosumab is a viable option in children with ABC refractory to standard treatments.

We retrospectively reviewed the medical files of paediatric patients given denosumab to treat ABC in any of 32 centres affiliated with the French Paediatric Cancer Society (Société Française du Cancer de l’Enfant, SFCE) and French Sarcoma Group (Groupe Sarcome Français, GSF-GETO). We identified 5 patients treated between March 2015 and June 2018. Median age was 8 years (range, 7–17 years). Pain was a symptom in all 5 patients and neurological deficits were present in 3 patients. Surgery was performed in 4 patients, either before (n=3) or after (n=1) denosumab therapy; the remaining patient had no surgery. Denosumab was given as monthly injections in a dosage of 70mg/m² for a median of 12 months (range, 4–23 months). The clinical outcomes and changes in computed tomography and/or magnetic resonance imaging findings were evaluated.

Abnormalities in calcium and phosphate levels secondary to the ABC occurred in 2 patients. At median of 24 months (range, 0–28 months) after denosumab initiation, all 5 patients were free of pain, and the neurological deficits in 3 patients had improved. Central remineralisation and cortical reconstitution were demonstrated consistently by the imaging studies.

Denosumab is a viable treatment option in selected paediatric patients with inoperable ABC. The immediate adverse effect profile is acceptable. A larger study with a longer follow-up would be welcome to further assess the contribution of denosumab to the treatment of ABC.

IV.