Silvia Ferrari, Neal Shiv Chawla, Michela Pierini, Imran S. Syed, William E. Mendanha, Emanuela Marchesi, Anna Paioli, Kumar Sankhala, Madhuri Sudan, M. Piccinni Leopardi, Prarthana Parthasarathy, Sant P. Chawla, Emanuela Palmerini, P. Picci, Palmerini, E, Chawla, N.S., Ferrari, S., Sudan, M., Picci, P., Marchesi, E., Leopardi, M. Piccinni, Syed, I., Sankhala, K.K., Parthasarathy, P., Mendanha, W.E., Pierini, M., Paioli, A., and Chawla, S.P.
Background Giant-cell tumours of bone (GCTB) are RANK/RANK-ligand (RANKL) positive, aggressive and progressive osteolytic tumours. Denosumab, a RANKL inhibitor, was FDA-approved for adults and skeletally mature adolescents with unresectable GCTB or when surgical resection is likely to result in severe morbidity. Data on long-term toxicity and activity of denosumab monthly ‘GCTB-schedule’ (120 mg per 12/year, 1440 mg total dose/year) are lacking. Methods Patients with GCTB receiving denosumab, 120 mg on days 1, 8, 15, 29 and every 4 weeks thereafter, from 2006 to 2015 treated in two centres were included. Long-term toxicity was evaluated. Results Ninety-seven patients were identified. 43 patients underwent resection of the tumour with a median time on denosumab treatment of 12 months (range 6–45 months). Fifty-four patients had unresectable GCTB's (male/female 23/31, median age 35 years [range: 13–76 years], 26% presented with lung metastases, 31% had primary tumor located to the spine, 63% were relapsed after previous surgery) with a median time on denosumab of 54 months (9–115 months). In the unresectable GCTB group, tumour control and clinical benefits were observed in all patients undergoing denosumab, whereas 40% of patients discontinuing denosumab had tumour progression after a median of 8 months (range 7–15 months). Adverse events Overall, six (6%) patients developed osteonecrosis of jaw (ONJ): 1/43 (2%) in the resectable group, 5/54 (9%) in the unresectable group, with a 5-year ONJ-free survival of 92% (95% CI 84–100). Only patients with prolonged treatment experienced mild peripheral neuropathy (6/54, 11%), skin rash (5/54, 9%), hypophosphataemia (2/54, 4%) and atypical femoral fracture (2/54, 4%). Conclusions Prolonged treatment with denosumab has sustained activity in GCTB, with a mild toxicity profile. The dose-dependent toxicity observed recommends a careful and strict monitoring of patients who need prolonged treatment. Decreased dose-intensity schedules should be further explored in unresectable GCTB.