Clinical, radiological and pathological outcomes following treatment of primary giant cell tumour of bone with Denosumab.

Background: Giant cell tumour of bone (GCTOB) is a relatively uncommon, benign, but locally aggressive neoplasm. Denosumab is a fully human monoclonal antibody with inhibitory effects on receptor activator of nuclear factor kappa-B ligand that has shown early promise as a possible treatment adjuvant for GCTB. However, much is still unknown about its current indications, long-term effects, the potential risk for rapid relapse and its involvement in sarcomatous transformation.

Methods: We analysed the outcomes of 154 patients with GCTOB. We assessed clinical outcomes via local recurrence free-survival, metastatic free-survival and sarcomatous transformation between those treated without Denosumab and those with neo-adjuvant Denosumab. Our radiological and pathological outcomes were assessed through independent specialist reviews.

Results: Four (19.0%) patients of the neo-adjuvant group had local recurrence of disease versus 16 (12.0%) patients in the surgery alone group; this results in a 3.62 times increased likelihood of developing local recurrence (P = 0.030). The median time to local recurrence was shorter for the neo-adjuvant group (421.5 days versus 788.5 days) (P = 0.01). There was no difference between Denosumab and the surgery groups in terms of metastatic disease (P = 0.45). Two patients in our cohort with GCTOB developed sarcomatous transformation, both were treated with Denosumab.

Conclusion: Our use of Denosumab tended to be for those patients who had surgically difficult tumours to halt the progression and allow easier resections. Of concern we noted a trend towards increasing recurrence rates with the potential risk for rapid relapse. Furthermore, two cases experienced sarcomatous transformation, which is a growing area of concern within the literature.