Successful treatment with denosumab in a patient with sacral giant cell tumor of bone refractory to combination therapy with arterial embolization and zoledronic acid: A case report

Giant cell tumor of bone (GCTB) is commonly treated with surgery; however, surgery of GCTB in the sacrum may be challenging due to the associated risk. A conservative approach may be selective arterial embolization or zoledronic acid (ZOL) treatment; however, there are currently no studies investigating the efficacy of combining these two treatments. Denosumab may also be used; however, to the best of our knowledge, there are no reports of a stepwise approach for the use of all three treatments in a single patient. We herein present such a case. A 32-year-old woman diagnosed with sacral GCTB was treated with selective arterial embolization for 3 months. No improvement was observed, and monthly infusions of ZOL were added (administered 2 weeks after each arterial embolization treatment). Ten months after the initiation of ZOL, there was still no improvement. The therapy was changed to denosumab 120 mg, injected subcutaneously once a month. By the third dose, the buttock pain had decreased and the patient became ambulatory. At 5 and 10 months, computed tomography scans revealed bone sclerosis gradually appearing around the sacrum. By 1 year, needle biopsy detected no neoplastic cells. At that point, the patient discontinued treatment, as there was hepatic function impairment due to a history of hepatitis B. Despite treatment discontinuation, the patient exhibited no further symptoms, there were no signs of progression on radiography, and surgery was not required. Our patient experienced treatment failure with selective arterial embolization. The combination of ZOL with selective arterial embolization also did not improve the patient's condition. Denosumab was found to be superior to both treatments, achieving tumor remission. The patient remains symptom- and disease-free. Further studies are required, but our results suggest that patients with unresectable GCTB who fail to respond to selective arterial embolization may benefit from denosumab treatment, but not from combination therapy with selective arterial embolization and ZOL.