Giant cell tumor: rapid recurrence after cessation of long-term denosumab therapy.

We report a case of rapid recurrence of a giant cell tumor (GCT) of the distal radius in a 24-year-old woman following the cessation of long-term denosumab therapy. GCT of bone is a histologically benign tumor with multinucleated giant cells on a background of mononuclear giant cells usually presenting as a well-defined epi-metaphyseal lytic lesion without sclerotic margins. Denosumab, a monoclonal antibody to the receptor activator of nuclear factor kappa-B ligand (RANKL), has proven to be an effective neoadjuvant treatment for GCT. The tumor in this case had demonstrated a good response with sustained control for over 2 years while on denosumab therapy. However, within 2 months of cessation of therapy, the tumor demonstrated rapid recurrence and progression with growth, osteolysis, and increased soft tissue component. Despite reinitiating denosumab therapy, there was progressive tumor growth and destruction, ultimately necessitating below-the-elbow amputation. This case illustrates the need for maintenance of denosumab therapy for GCT of bone or definitive surgical treatment prior to its cessation.