Endocrine Abstracts

JOINT1060

Introduction: Giant cell tumour of the bone (GCTB) is a rare tumour that is usually benign but can be locally aggressive. GCTB accounts for about 15–20% of all benign bone tumours and typically arises from the epiphysis of long bones. Surgical removal of GCTBs remains the gold-standard treatment. However, there have been a few reported cases where the tumour originated from the sphenoid bone, and in these instances, total surgical removal is often not feasible due to the proximity of critical anatomical structures. More than a decade ago, denosumab was approved as an alternative treatment for this condition.

Case Report: In May 2018, a 16-year-old female patient presented with severe headache, dizziness, vomiting, double vision and right-sided retrobulbar pain. A pituitary MRI demonstrated a large sellar mass that occupied the pituitary gland and invaded the right cavernous sinus. In June 2018, she underwent a paraseptal, transsphenoidal adenomectomy. However, the histological evaluation revealed only physiological pituitary hyperplasia. In August 2018, she returned with alarming symptoms. Following a thorough endocrine examination, she was diagnosed with severe panhypopituitarism and appropriate hormone replacement therapy was initiated. In September 2018, a follow-up MRI showed significant tumour progression, prompting a second surgical intervention. At that time, the tumour measured 33 x 28 x 51 mm, invaded the right cavernous sinus and elevated the optic chiasm. No visual disturbances were detected during the ophthalmological examination. The histopathological results from this surgery confirmed the presence of GCTB. Subsequently, she began treatment with denosumab. Five months later, a new MRI indicated a 40% regression in tumour size. Denosumab therapy was continued until December 2021, during which stable disease was observed both clinically and radiologically, leading to the discontinuation of the drug. However, in July 2022, a follow-up MRI revealed significant tumour progression and denosumab therapy was reinstated. To date, the patient receives 120 mg of denosumab every four weeks, and there has been no further progression of the tumour.

Conclusion: To our knowledge, this case report presents the longest use of denosumab therapy with efficacy and safety for GCTB in the sellar region. We have not observed any side effects from denosumab throughout the six-year treatment period. However, further research is necessary to determine this thyrapy’s optimal long-term dosage and duration and to identify other treatment targets that could provide similar tumour control.