Malignant Giant Cell Tumour of Bone: Clinicopathologic Characteristics, Treatment Outcomes, and Real-World Experience from aTertiary Sarcoma Centre

Background : Giant cell tumor of bone (GCTB) is typically benign, but a small subset develops malignant GCTB (MGCTB), arising either de novo (primary) or after prior benign disease (secondary). This study presents real-world outcomes of systemic treatment in MGCTB. Methods: We retrospectively analysed adults (≥18 years) with histologically confirmed primary or secondary MGCTB treated at our tertiary sarcoma clinic (2018–2025). Diagnosis was based upon expert pathology opinion and H3F3A IHC. Clinical, pathologic, treatment, and response data were collected and analysis was done using SPSS v.30. Results: Twenty patients (median age 41 years, 65% male) were analysed: 7 (35%) PMGCTB and 13 (65%) SMGCTB (median latency 84 months). Tumours were mainly appendicular (70%), most often distal femur (45%). Around half (8/20; 40%) were metastatic at presentation, mostly to lung. Most common histology was osteosarcoma and UPS. Local control was achieved with wide excision (12/15, 80%), amputation (1/15, 7%), intralesional surgery (2/15 13%). 18 patients (90%) received systemic therapy (median 5 cycles, predominantly doxorubicin-based (16/18, 88%). Neoadjuvant chemotherapy induced responses in 2/3 patients, allowing R0 resection. In the adjuvant group (n=6), only 2 patients remained disease free at the end of follow up. In the palliative chemotherapy cohort (n=7) responses were limited (2 PR, 1 SD). Pazopanib (n=8) produced clinical benefit in 4 patients(50%). Subsequent lines (gemcitabine–docetaxel, eribulin, cisplatin regimens, cabozantinib) showed modest, short-lived activity. The median overall survival was 60 months, with the estimated 12-month OS rate of 65%, and the 60-month OS rate of 42.6%. Conclusions: This study represents one of the largest contemporary real-world evaluation of chemotherapy in MGCTB, providing novel real world insights into response and survival. Systemic therapy and targeted therapy offer modest benefit.