Use of denosumab in aggressive spinal osteoblastoma

Introduction. Osteoblastoma is a locally aggressive benign tumor affecting skeletal bones and most commonly seen in the spine. Most complications arise during treatment of stage III osteoblastoma per the Enneking classification characterized by fast growth and intra- or extracompartmental lesions. Despite the use of modern navigation technologies, intraoperative orientation of a surgeon relative to the soft and bone tissues remains the most important factor of successful and complete resection of the pathological lesion in case of osteoblastoma. The use of denosumab as a neoadjuvant agent promotes sharper differentiation of the tumor from intact bone tissue which makes tumor resection easier. Additionally, this drug can be used in the postoperative period to decrease the risk of recurrence and for unresectable forms of the tumor. 
Aim. To evaluate the effectiveness of denosumab in the treatment of aggressive  spinal osteoblastoma.
Materials and methods. The results of treatment of 6 patients (5 men, 1 woman) with aggressive stage III osteoblastoma per the Enneking classification who received treatment at the 11th Division of the National Medical Research Center of Traumatology and Orthopedics named after N.N. Priorov between 2021 2025 were analyzed. In all cases, diagnosis was histologically confirmed at the biopsy stage. Tumors were located at different levels of the spine: in 2 cases, in the cervical spine; in 3 cases, in the thoracic spine; and in 1 case, in the sacrum. All patients were prescribed denosumab (off-label). Density and volume of the tumor was evaluated using computed tomography and Gamma Multivox software.
Results. Analysis of the main effectiveness endpoints showed that the use of denosumab is associated with increased tumor density and significant decrease of pain in all patients. Additionally, a trend towards increased tumor volume per computed tomography was observed which can be explained by improved visualization of the tumor margins due to sclerotization of the soft-tissue component.
Conclusion. Neoadjuvant therapy with denosumab showed its effectiveness in aggressive osteoblastomas which opens new options for treatment of unresectable and recurrent tumors.

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