Stereotactic body radiotherapy for lung metastases in a patient with giant cell tumor of bone: a case report and literature review.

Giant cell tumor of bone (GCTB) is a rare borderline tumor which can develop lung metastasis. Guidelines for patients with multiple pulmonary metastases recommend systemic therapies, such as denosumab and interferons (IFNs). However, when both of these treatment approaches fail, no satisfactory options are available. Thus, additional treatments for GCTB after failure of standard treatment would be beneficial. Here we present a patient with GCTB and multiple pulmonary metastases who was treated with stereotactic body radiotherapy (SBRT) after failure of surgery, denosumab, and bisphosphonates (BPs). This is the first well-documented report of a patient with metastatic GCTB who received lung SBRT after the failure of systemic therapy and achieved a favorable response. Some of the patient's pulmonary metastases were treated using SBRT (44 Gy/4 F). The long diameters of the irradiated nodules decreased 58.2% from baseline in the 30 months after SBRT. Moreover, the peritumoral volume of another nodule also shrank by 29.1% after receiving a low-scatter dose of 7.6 Gy/4 F, which was too small to have induced tumor regression. No obvious adverse events were observed during SBRT or in the follow-up period. Our case provides clinical evidence that SBRT may be a safe and effective method to treat metastatic GCTB and can produce a low-dose radiation-induced abscopal response, suggesting that immune responses can contribute to GCTB regression. In addition, we reviewed publications regarding treatment recommendations, the prospects for SBRT application, and possible effects of abscopal responses on GCTB.