Morphologic Changes After Denosumab Therapy in Patients with Giant Cell Tumor of the Spine: Report of Four Cases and a Review of the Literature

OBJECTIVE: To evaluate the quantitative, radiologic, morphologic, and histo-logic effects of neoadjuvant denosumab treatment (DT) on 4 patients with spinal giant cell tumor of bone (GCTB) and determine the tumor shrinkage effects of DT for spinal GCTB. METHODS: The morphologic changes in the 4 patients with spinal GCTB who underwent total spondylectomy after neoadjuvant DT at our institution were retrospectively analyzed using computed tomography. Osteolytic tumor volume, vertebral body height, maximum anterior and transverse diameter, and mean area of the spinal canal occupied by the tumor were evaluated. RESULTS: In all patients, osteolytic tumor volume decreased by 81.2% and vertebral body height decreased by 87.4% on average following DT. In 3 of 4 patients with osteolytic lesions and a thin cortical rim, vertebral collapse had progressed after DT. Conversely, vertebral collapse was not observed in one patient with adequate anterior cortical bone. Two patients showed a mean decrease of 96.7% in the maximum transverse diameter, whereas 2 had a mean increase of 109% due to vertebral collapse. The mean area of the spinal canal occupied by the tumor reduced from 56.1% to 15.1%. CONCLUSIONS: In all patients, osteolytic tumor volume decreased after DT. This tumor shrinkage effect of DT may increase the mechanical stress on the thin cortical rim, leading to the acute collapse of the affected vertebral body if it consists mostly of osteolytic lesions. The presence of adequate anterior cortical bone could prevent acute vertebral collapse after DT.