1966P - Extending the interval of denosumab treatment for unresectable giant cell tumor of bone

Background

The necessity of life-long denosumab injection may cause several problems for unresectable giant cell tumors of bone (GCTB). The efficacy and safety of extending the interval of denosumab treatment (de-escalation) for GCTB were investigated.

Methods

The medical records were retrospectively reviewed for nine patients with GCTB that were either unresectable or resectable, but not those of resection candidates, who received de-escalated denosumab treatment at a single institution since 2014. The median age at initial denosumab treatment was 44 years and tumor location consisted of 5 sacral spines, 2 femurs, one thoracic, and one lumbar spine. The denosumab treatment interval was gradually extended to every 8 weeks, 12 weeks, and 24 weeks. The radiographic changes and clinical symptoms were assessed during standard and de-escalated denosumab therapy.

Results

The denosumab interval was de-escalated after a median of 12 (8-16) months of standard 4-weekly treatment. The median duration of de-escalation treatment was 46 (9–75) months. Imaging showed that a good therapeutic response obtained with the 4-weekly treatment was sustained during the 8-weekly and 12-weekly treatments. According to the MD Anderson criteria, GCTB treated with de-escalated denosumab therapy resulted in a complete response in one patient and a partial response in eight patients. The extraskeletal mass reduced significantly with standard treatment, and tumor reduction was sustained during de-escalated treatment. The clinical symptoms significantly improved with standard treatment and remained improved during de-escalated treatment. Two patients remained stable during the 24-weekly treatment, while one developed local recurrence. Eight of the 9 patients had received de-escalated treatment at the latest follow-up. One developed malignant transformation and pulmonary metastases.

Conclusions

12-weekly de-escalated treatment of denosumab can sustain symptomatic relief, tumor reduction, and new bone formation achieved with standard treatment, resulting in effective maintenance treatment in patients with unresectable GCTB. 24-weekly treatment can also be selected, with careful attention to local recurrence.

Clinical trial identification

Editorial acknowledgement

Legal entity responsible for the study

The authors.

Funding

Has not received any funding.

Disclosure

All authors have declared no conflicts of interest.